title_body: What was the cause for the current overwhelming popularity in the brighter, more acidic coffees?
upvoted_answer: I think there are a number of factors influencing the current situation.
  
  
  The rise of micro/small and home roasters.  This allows people access to fresher coffee.  The acidic and bright notes in coffees tend to fade quicker than roast notes.  Meaning these bright notes are more readily available to the consumer.
  Changes in coffee processing.  Different process methods favor different flavor profiles.  Dry Process (the oldest) favors less bright and more bodied flavors.  Newer processing methods enhance bright flavor profiles.
  The rise and market dominance of large chain roasters.  These companies tend to roast dark because it is easier to hit a consistent flavor profile which lasts longer (important for shipping), but it sacrifices the origin flavors which are varied greatly and available.  They have given dark roasts a more McDonald's character among consumers (consistent, but not high quality). 
  
  
  This is not to say that dark roasts are bad.  But they have partially been given a bad rep by large chains who are using them to maximize profit, and not flavor.  Home and microroasters now also have unprecedented access to a HUGE variety of beans that years back would have been out of reach.  This means that companies can cheaply distribute very high quality beans with extraordinary flavor profiles when roasted at a lighter level.