You're right. Just comparing the phenomena. I'm sure if phones could record video back in 2001, people on those planes would have been filming the hijacking the same way. It's the same kind of thing just happening in a different era.They didn't do anything because they will have remembered the hijackings back in the 1970s, when the passengers would almost always be released, and the terrorists had control of the cockpit, which gave them a vastly more devastating threat than a gun: the ability to crash the plane.
The passengers attempted to storm the cockpit on the last plane almost certainly because it was significantly later than the others. News of the other planes had come through to those with mobile phones and they realised that they had nothing to lose.
I have a hard time getting upset over people not being a hero in either instance because being a hero is fucking hard and not everyone can just spring up to do it.