I’ve seen plenty of videos showing a plane losing power, it doesn’t translate to just falling out of the sky like this. Wouldn’t you have to lose control of all the flight control surfaces? flaps, etc..?
...unless he had a heart attack or something and slumped over the yoke?
That was my guess.
I saw an expert video interview yesterday. It is very likely that the plane iced up and the pilot did not notice it in time leading to a stall. The stock auto pilot on those planes does not manage the throttles. So if the auto pilot was engaged then it could have kept pitching the plane up(Trying to maintain altitude) causing a loss of air speed until it stalled. It is up to the pilot of monitor the throttles and air speed. There were ice warnings in the area he was landing.