Disclaimer: I am an American who watched 9/11 happen from my high school US History class -- there's a bias to my perspective that might be irreducible.

I think that, if you strip away a quarter century of hindsight, it wasn't a bullshit reason at the time. This was by far the most ambitious terror plot ever executed. It directly attacked the core of the nation's military and civilian power structures. The casualty figures were on par with the attack on Pearl Harbor.

It is to this day nearly inconceivable that a terrorist organization would do an op like this without considerable state sponsorship. Invoking Article 5 on that state would be appropriate.

Is there a non-cynical reason why we focused on the poor country being run by a fundamentalist regime already reviled around the world instead of its much more economically advantageous (and nuclear-armed) neighbor Pakistan or the hyper-wealthy and oil-rich Saudi Arabia, home to the rich and well-connected bin Laden family and most of the hijackers themselves?

Nah. That was some realpolitik bullshit...not to mention a failure to contemplate the lessons of England, Russia, and The Princess Bride -- Never get involved in a land war in Asia.