Captain not seated? FA's not seated? No warning from cockpit? No Mayday? These pilots were in the swamp very quickly perhaps wrestling to regain control, g forces could easily have prevented anyone from donning flotation. If no air at altitude, consciousness is lost at 40 seconds tops.
Forgive me, since this makes me rather queasy, but wouldn't the autopsies indicate whether the victims were already unconscious at the point of impact, verses still conscious? If your theory is that the aircraft was compromised in some fashion as to render the pressurization system inop, consequentially incapacitating (everyone) and given it took several minutes to hit the ocean, I'd would have thought that there would be a number of tell-tale symptoms during autopsy? Also wouldn't one or two oxygen masks have been found? Perhaps they were....?
-GY