Whenever there is an industry-wide expansion, the regionals are often the ones hit hardest.
Given the rate at which BA/Jet2/EZY are recruiting and running selections, it's not surprising there are lots leaving.
There's more to life than money, but moving to a short haul jet from a regional turboprop makes life a lot more comfortable. Even going from a prop CPT to a jet FO is likely to see a pay rise.