"Something made them make those decisions."
From the CVR and their subsequent actions it appears that the UAS indications with sudden AP disconnection and reversion to alternate law took them completely by surprise. This sort of behavior from the aircraft was something totally unexpected and for which they were emotionally unprepared. They were "gobsmacked" and and what training they did have, just went out of the window - no actioning of lists, no attempt at analysis, no rational response at all, just fiddling in increasing confusion with the primary flight controls as more and more warning messages flashed and audible alarms blared on and off as the situation deteriorated.
Finally they were completely lost as the PF admitted ("I have no control of the aircraft") with no coherent mental image of the situation - even the altimeter winding rapidly down seemed unreal, and the Captain appeared on the scene far too late to compose his own perception or take any meaningful action.
A tragedy composed of overconfident automation design compounded by pilot complacency and inadequate systems training.