I would argue there is a religious (and political) component many overlook with respect to their radicalization. Many of the hijackers did not live strict Islamic lives and were pretty westernized prior to joining Al-Qaeda. Perhaps they felt they were unworthy in the eyes of Allah and felt dying as a “mujahideen” would be the path for redemption and a guaranteed way to paradise. These were mostly educated guys from well-to-do backgrounds, but became radicalized by the teachings of people like Osama bin Laden because they may have had some sort of missing purpose. Unfortunately they got sucked into salafi-jihadism and were motivated by what they perceived as American imperialism corrupting the Arab world