My nephew sent me this last month ...
Airbus Stall Training:
https://www.youtube.com/watch?v=4WuPoVjOXLY
... and posed this simple question: "If they knew they were in a stall, even I would know what to to do - and if they didn't realize, how is that even possible?"
Beats me.
edit to add: What Clandestino said, but with less fibre