Wasn't part of it that before 9/11 a hijacker using the plane as a weapon or wanting to kill everyone wasn't the expected, and thus the assumed "best" route was to comply (as not to provoke the hijacker to start killing hostages to increase the pressure), go wherever they want and hope law enforcement will sort it out?
E.g. the cited Cuba hijackers didn't very often kill people. Some of them might have given up when unable to get to flight crew, but others might have used more force to get what they wanted.
That's always been my understanding of it. Hijackings were common in Europe for example and that's how it almost always went down. (Not too familiar with the history of hijackings in USA, but sounds the same.) Then we saw the change right on 9/11 when passengers on UA93 learned their hijackers intended fate and fought back.
E.g. the cited Cuba hijackers didn't very often kill people. Some of them might have given up when unable to get to flight crew, but others might have used more force to get what they wanted.