How was this airline (statistically) never had a fatal incident?
First of all, Ryanair has more than 700,000 flights per year now, but not during their entire 35 year existence. The total number of flights you give is therefore too high.

Assuming aircraft accidents are purely statistical (which is not true, of course), one can estimate the number of accidents you expect using a Poisson distribution: the probability of having $ k $ incidents with $ \lambda $ expected incidents is given by

$$ P(k) = e^{-\lambda} \frac{\lambda^k}{k!} $$

To get the expected number of incidents, we take the overall accident rate of 1 in 2.5 million flights (aviation-safety.net, for 2018, has been higher during the last 35 years) and multiply it with the total number of flights. For 25 million flights this would be $ \lambda = 10 $. This results in in a probability for 0 accidents of only $ P(0) \approx 0.004 \% $. Even when assuming 12.5 million flights in total (as suggested by David Richerby in the comments assuming a linear increase from 0 to 700,000 flights per year), one still obtains $ P(0) \approx 0.67 \% $ with $ \lambda = 5 $.

This means Ryanair is indeed safer than the average airline flight world wide, but so are many other EU or US airlines. Safety is not just a statistical coincidence, regulations are very strict in Europe and training is good resulting in higher than average safety records.