The Italian's first season in charge, following an appointment greeted with a wave of indifference, ended with a success that defied history, logic, the odds and the game's natural financial order, as he turned a Leicester team that narrowly avoided relegation into champions.
The day Ranieri, in a stadium cloaked dramatically in storm clouds but fuelled by undiluted emotion, led blind tenor Andrea Bocelli to the centre circle to start the title celebrations seemed an age away as Leicester brutally sacked the man who gave the club its greatest moment.
So how has football's greatest fairytale descended into a nightmare in just nine months?
It is almost the thought that dare not speak its name amid the wave of shock, outrage and disgust at Leicester's decision to ruthlessly dismiss the hugely popular 65-year-old, who won the hearts of all supporters with his good humour, class and dignity as he led the Foxes to the title.
Match of the Day presenter Gary Lineker, a former Leicester and England striker, tweeted: "After all that Claudio Ranieri has done for Leicester City, to sack him now is inexplicable, unforgivable and gut-wrenchingly sad."
Lineker echoed the thoughts of the majority who aired their views publicly - but is there actually method in what many see at the madness of the club's Thai owners?
Leicester's fall has been more dramatic than anything they could have foreseen in their worst nightmares. A win for any of Sunderland, Crystal Palace and Hull City this weekend would put the Foxes in the relegation places. Wins for all three and they would be bottom by the time they face Liverpool on what will now be a highly charged occasion at the King Power on Monday.
After 26 games last year they were top on 53 points, two ahead of Spurs. This season they are 17th after 25 games, with only 21 points. Last season they had lost only three games compared with 14 in this campaign, and conceded only 29 goals compared with 43 this term. Indeed, they only conceded 36 in the entire 2015-16 season.
The difference is stark and, very clearly in the opinion of Leicester's owners, dangerous.
The clear and present danger was the threat of relegation, as stated by vice-chairman Aiyawatt Srivaddhanaprabha when he said: "It was never our expectation that the extraordinary feats of last season should be replicated this season. Survival in the Premier League was our first and only target at the start of the campaign."
Would Leicester fans have thanked the board for being sentimental all the way into the Championship? Cut away the romance, sentimentality and the memories of last season and they will feel this decision has been taken to stave off the most dramatic fall of any Premier League champions.
It will still, however, be a very hard sell given Ranieri's history-making effort last season.
No manager can ever be unsackable - but Ranieri's reserve of credit was as close to limitless as it gets after performing a sporting miracle to win the title last season.
It is the second season in succession a Premier League-winning manager has failed to survive the following campaign. Jose Mourinho was sacked by Chelsea after he was a champion in 2015.
Mourinho, however, was at a club with a high turnover of managers that had enjoyed huge successes - he had not pulled perennial strugglers from near the bottom to top of the table in the blink of an eye.
Plenty will regard Leicester's treatment of Ranieri as a cut-throat act from an ownership who should wake up and give him thanks every day for giving them a success and a story they would have regarded as fantasy when they appointed him.
Ranieri took Leicester from 14th to first with a style built on solid defence, fierce organisation and a thrilling counter-attacking style based around Jamie Vardy and Riyad Mahrez. He was the master man-manager, taking all the pressure and letting his players fly.
There is no doubt there is some real unease among Leicester's fans about Ranieri's sacking, and how it reflects on the image of the club supported so fervently by neutrals - and just about any club that could not win the title - last season. Leicester were having relegation wished on them on social media on Thursday by those whose hearts they won last year.
The manner in which Ranieri has been shown off the premises has prompted questions about basic loyalty and decency in football, and how a manager who made Leicester a worldwide feelgood sports story can be treated in such a way.
And surely his success last season proved he could still keep Leicester in the Premier League?
Ranieri is experienced, up for the fight and had a reservoir of goodwill last season to call on.
Sadly for this most amiable and classy of men, the reservoir ran dry on Thursday.
The vote of confidence is always regarded as 'dreaded' - but Leicester's for Ranieri may come to be known as notorious.
It was on 7 February, 16 days before the axe fell, and after a 3-0 home defeat by Manchester United, that they announced "unwavering support" for the Italian, stressing boardroom loyalty further by adding "the unprecedented success achieved in recent seasons has been based firmly on stability, togetherness and determination to overcome even the greatest of challenges".
So what has happened since to effect such a change?
Leicester beat Derby in an FA Cup fourth-round replay the following day but then turned in a dreadful display to lose 2-0 at relegation rivals Swansea before going out of the FA Cup with an under-strength team at League One Millwall.
A Champions League last-16 loss at La Liga powerhouses Sevilla was a relatively acceptable result but the performance was poor - were Leicester's owners simply seeing no signs of improvement?
Grim reality, not to mention fear, may also have descended on the boardroom at the sight of Hull City showing progress under Marco Silva as the club felt the cold hand of relegation on its shoulder.
What is clear is something has changed dramatically, and it is the ominous prospect of going from champions to Championship in 12 months.
Leicester's players would have done well to avoid social media after news emerged of Ranieri's sacking. There was widespread sympathy for the manager and scathing criticism for the players whose standards have fallen through the floor.
Something has been amiss from day one this season after a summer of big new contracts for the title winners and one very crucial departure.
Jamie Vardy, top scorer with 24 goals last season, rejected a £22m summer move to Arsenal to sign a lucrative new four-year deal. The Gunners may regard this as a bullet dodged as he has scored only five league goals this season, including a hat-trick in the 4-2 win against Manchester City.
PFA Player of the Year Riyad Mahrez, coveted across Europe, signed a four-year contract, while goalkeeper Kasper Schmeichel, wanted by Everton, signed a five-year deal along with midfielder Danny Drinkwater.
Mahrez scored 17 league goals last season but has contributed only three this term, while Drinkwater has failed to reproduce the form that earned him an England call-up.
Leicester's players appear to have lost the hunger, as well as the element of surprise, that enabled them to climb the mountain last season.
And in some cases, such as captain Wes Morgan and Robert Huth, they have simply reverted to the workaday Premier League central defenders they were before they were carried along with an unstoppable momentum last season.
There has also been sniping behind the scenes that has not helped Ranieri, with whispers emanating from inside the camp that he had become distant from his backroom staff amid growing unrest from his management team and players.
The same stories came out about Ranieri's tactical approach - giving the impression the players were happy to take the acclaim last season but were only too willing to point the finger of blame at their manager after it went wrong.
He was also subjected to a public attack from striker Leonardo Ulloa, who accused Ranieri of betrayal as a move to Sunderland was falling through.
If these players have been using Ranieri as a shield for their own shortcomings, then this has been removed. They now have no excuses or scapegoat.
And yet the biggest factor of all may be a player who is no longer at Leicester.
N'Golo Kante, Football Writers' Association Footballer of the Year last season, took his relentless tackling, work-rate and guile to Chelsea in the summer in a £32m deal. The Foxes have never been the same - whereas he is on course for another title at Stamford Bridge.
Once the shockwaves have subsided, Ranieri will be remembered as the manager who gave Leicester, the city and the football club, its greatest sporting moment. He made Leicester a worldwide good news story.
He will be remembered as a man of manners and dignity but with a steel behind the smile that enabled him to lead the Foxes to perhaps the most unlikely triumph in British sport.
Ranieri will also be remembered by many as someone who was treated shabbily and without gratitude at the end - an example of how sentiment will never exist in football.
In the final analysis, though, he will remembered at Leicester as a good man who performed a great feat. And will be remembered forever.
It must be assumed Leicester's owners have a new man in mind to make such a seismic move as sacking Ranieri.
Combustible former manager Nigel Pearson was even linked with a return, but one live contender appears to be Ranieri's compatriot Roberto Mancini.
He is available, had a short spell as a Leicester player in 2001 and has Premier League experience as a manager. Mancini led Manchester City from December 2009 to May 2013, winning the FA Cup in 2011 and their first title in 44 years 12 months later.
Whoever is next, the first priority is safety rather than emulating Ranieri's title-winning feats.
When Claudio Ranieri - surrounded by his triumphant Leicester City squad - lifted the Premier League trophy at the King Power Stadium on 7 May last year, it concluded arguably the greatest story in British sport.