From my read and see it looks like the problem was the aftermath of the engine event with visible and acrid smelling smoke in the cabin upsetting the passengers and CC. Thus the puposedly dropped masks to ease the choking feeling.
Yes the "BRACE BRACE probably added to it and the cap was the bloke who opened an exit by himself.
Not sure how long it takes to clear a cabin of visible smoke from an engine internal fire. Seems too long in this case