bin Laden and al-Qaida talked a lot about their motivations. For one it was disgusting to them that the house of Saud bowed and scraped for the crusaders in Washington, and so was the rather arbitrary abuse of Afghanistan.

They also were under the delusion that the US was a democracy, and hence the general population could be held responsible for the actions of its leaders. Understandable if they had mainly been exposed to US/Occidental state propaganda.

Today I don't think anyone would be inclined to hold such a belief.