I believe many accidents are caused by technical issues, weather and turbulent. As well as pilot errors.
We can completely rule out weather and turbulent in this case.
Jammed stick is high probability in this accident in my opinion. It also explaines the delay in decision to bail out while trying to unjam the stick. You can find on RAS many stories on jammed controls from one reason or another. We only know about those which the pilot survived to tell.

Ramy