because of a locked cockpit door

Door wasn’t locked and had nothing to do with the crash. In fact a flight attendant managed to get into the cockpit and turn the plane from a populated part of Athens, likely saving lives shortly before it fully crashed

The plane simply never pressurized and literally as the co-pilot realized what was happening hypoxia took them and the captain, all because a switch could turn pressurization into a manual override and there was no warning before takeoff that it was that way