In reference to the passengers, now we need to go back to your term, deploy. Masks will deploy automatically at a cabin pressure altitude of 14,000 feet or if manually deployed by the cockpit crew.
Don’t assume the airplane will stall at Flight Level 450. I got into it with another Freeper on that topic. I’ve taken airplanes above their service ceiling on a number of occasions. The retired captain that called Rush confirmed that a B777 can sustain flight at FL450. A service ceiling is defined as the highest altitude where an aircraft can maintain a fifty foot per minute climb.
And like you, I don’t put complete faith in the FL450 number until we know more about the source.
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.