Training Training Training...
There is no mystery.
1/ a pilot nose up
2/ he stalled his plane and didn't alert the captain nor did he communicate
3/ he didn't recognize his fault although his instruments gave him all the necessary information (the lack of speed data is a consequence of the stall not the cause)
That's all.
Pilots are here to pilot the planes that are given to them (OK : their opinion is welcome).
I play golf : every 3 month I need 3 hours of practicing my 3 iron to be able to do something with it.
To pilot is a sport : it needs training and training and training.
That's why there are captain and cadet. Champions and losers.