Let's just say that Al Qaida had an easy time recruiting men with a grudge against the U.S. The western worlds 'decadent' lifestyles are just a way for Al Qaida to dehumanize them.
That said, I bet Mohammed Atta and Osama Bin Laden also have their reasons besides idealistic ones to despise the western world.
- Osama never took responsibility for 911. His multiple speeches he gave recorded in caves after 911 were incorrectly translated and heavily redacted for political purposes. E was just perfect to be framed. Anyone speaking Laden's language can hear him speaking that his family were doing business with Bush family (proven fact) for decades and he would never be competent to carry such an attack. Unfortunately, most videos of him speaking without overlapping loud audio vanished and any translation you find you can barely hear his native language. But you can find interview with people that were asked to translate his words ad they were pretty angry that everything got twisted.
- ibn Laden was on FBI top list but never for 911. As far as I remember he was most wanted for some huge oil fraud he performed while his family did work with Bushes.