Since you can see the door you know it’s in the proper position. The fasteners securing the plug are there to insure the door stays in the proper position when the aircraft is not pressurized. They are not structural to hold the door against the internal pressure. The plug design does that. I would place a large bet most or all of those fasteners were missing. The door shifted a bit. This appears to have started the day prior based on reports. Once it move enough to clear the lugs it simply fell out. The aircraft was actually barely pressurized when they lost the plug.