The difference between what you think vs what is could possibly cover the Atlantic. Not only is that pure speculation, it's tangential to the current issue. Bottom line line is that you have no clue what Bin Laden's motivation or intentions were. You weren't his psychologist, his priest, his cleric, his confidant, his best friend from high school, or even a casual acquaintance. Bottom line is whatever his motivation, we knew far in advance of 911, he was a terrorist leader we wanted to take out. Clinton was given the keys to just that, but instead......well history has demonstrated just how horrid a mistake that turned out to be. And per the Professor's parameters, the height of incompetence.
I haven't got certainty , but I do have clues.
Osama Bin Laden prepared for the fight he wanted , he had stocked up hiding places all over Afghanistan. Afghanistan being a good choice for being remote to the US, rugged and inhospitable
He sent men on suicide missions to irritate the USA. Bombing military and civilians in the Kobar towers ,The USS Cole and in the Kenyan and Tanzanian US embassies. Airliners were attacked and the World Trade center of course.
Immediately before the attacks of 9-11 the main leader of the opposition to the Taliban was assassinated by Al Queda suicide bombers who were pretending to be media interviewers. This was probably part of a deal and a plan to fight an insurgency with Talib help. I expect that Al Queda members that were able to convincingly imitate journalists were a valuable asset to be spent this way.
These and other clues make it seem that Osama Bin Laden had a long term plan and had laid preparations , hidden supplies and made alliances for the purpose of a long term insurgency.
“When people see a strong horse and a weak horse, by nature, they will like the strong horse” Osama bin Laden 2001
http://en.wikipedia.org/wiki/The_Strong_Horse In 2001 Osama Bin Laden thought his plans were coming together.
After a few years of quagmire type war , he would declare victory and return to his home as a Hero who could not be denied a role of leadership, because he would have proven his strength.
What he really wanted was a righteous Arabia, but just expelling all the Americans would not have been enough, he wanted more righteous leadership. I don't think he would have minded being Caliph himself either.