Your other suggestion that he tried to manipulate the switch while passing out and locked the door accidentally also is so unlikely that it borders on fantastical delusion. The default setting for the switch is a mode that magnetically locks the door when it closes, just like a door on a latch. In this mode, anyone entering their valid access code from outside, will gain entry in a few seconds if no action is taken from inside the cockpit. In other words, the default setting of the switch would have been enough to allow the pilot or crew to gain access in plenty of time to save the plane.
If that weren't enough, ADS-B data shows the co-pilot also reset the auto-pilot to 100 feet. An action that requires several very deliberate steps. It's very much looking like this guy just wanted to crash the plane.