One of the lessons of this paper is that there is no one way an individual can be radicalized or recruited. It could be propaganda playing on misguided idealism, like Dakhlalla spoke of, hours spent studying extremist ideology online like Hasan, or being separate from and not assimilating into society, like Awlaki chose.
The Washington Face of Islamic Extremism: Saudi Arabian and Iranian Use of U.S. Lobbyists and Other Proxies to Disrupt Decisive U.S. Decision-Making
Iran and Saudi Arabia are both exporters of extremism that fuels kinetic terrorist attacks. These countries are uniquely dangerous.