That said, even with the trim the way it was, the extreme attitude was being held with the elevators - letting go should have brought the nose down to some degree
Dozy, I don't think that is correct. Letting go would cause the aircraft to hold an attitude as long as it was above stall speed. Below stall speed it will bobble its nose up and down. It needs nose down input on the controls for a significant period of time or actually running the trim down manually to have a hope to recover.
The elevators have some influence, but the THS and the pitch up moment from the engines' thrust hold the trump cards.
The PF didn't actively hold the nose on the level flight pitch attitude when he took control and all bad things flowed from that.
When the nose tried to fall through at the stall, the PF actively fought it and that is the reason for most of his nose up input after the stall. Do you agree?