Sure, sure there’s the zealous religious beliefs, but it seems to me that there is a lot of similarities between the young people around the world (Americans, British, etc.) and those people that have joined gangs here in the US.
Most people that join gangs, don’t do it because they want to become thugs, deal drugs, and carry guns…they do it because they want to belong to something. Their family life doesn’t give that sense of belonging. I think that is why a lot of people join ISIS, so they can belong, so they can feel wanted and loved. The radical agenda is just part of the price of belonging.
If we as a society (globally) were better at making our children feel loved and accepted, I think there would be fewer recruits for these types of organizations.
Social Identity Theory, and how it relates to inter-group conflict discuss this if you want to research it. It deals with how people form an ingroup and come to outgroup hostility.
An interesting component, I think, is that humans have a need both for inclusion and differentiation. When those are threatened, violence is likely to occur. With all the upheaval in the area, I think it’s possible to imagine that the group in which they previously felt included shifted, as did the groups from which they differentiated themselves. To maintain a sense of self, they would have to redefine their ingroup, and redefine how they are different from the “other”, I think.
Poor young men who fall prey to these organizations are often enticed by money given to support their families. Mothers of suicide bombers have been given lump sum payments for “donating” a child to the cause.