Ahh - bottom hinge - now that I have a name for them:
I would not expect the bottom hinge to be in place for the substitute fixed door.
Seeing in the video that they don't have moving latches, the exit version of the doors are slid up to unalign the retaining features. Without the operating lever having someone pry the door up against the pressure it should not have moved.
Putting on a speculators cap - there were fatigue cracks in the retaining features / fingers on the door. Had only one let go I would not expect the door to do more than leak loudly. But if several had cracks then when one finally crossed the finish line the rest go in a rapid cascade.