A double engine flame out is highly unlikely as is the no auto feather scenario.
What is more likely is poor handling technique on the initial flame out leading to overuse with ailerons to maintain directional control, this is all due to an over realiance on the "new" auto rudder trim.
Seen it many times in the sim and when that rudder snaps out its not pretty.
All that said these comments are in no way saying that's what has occurred I'm not here to point fingers or do the I know why game. It's a very sad accident for all involved.