However, it's my understanding that it's a bit more demanding to fly at that altitude than at lower flight levels and easier to get into trouble.
And, if there was a fight of some sort for control of the a/c, or if it did stall as some speculate, then it could have stalled due to the engine, trim and/or control settings or some other reason, especially that high.
Lots to speculate about with no real info to go on other than our recent history with allah's friends and pilots.
Correct, an airplane can stall at any attitude, altitude, or power setting.
Sometimes my newbie co-pilots want to hand fly at high altitude. It is more difficult because the air is thin, so it is harder to maintain heading and altitude. But the autopilot handles it very well.
A stall at that altitude would take a significant amount of altitude to recover.