I would have to disagree with you there…
It had everything to do with religion—or at least their interpretation of it. The same thing with Hamas.
Obviously, not all people interpret religion or their holy books the same way—as Westboro Baptist Church claims that “God hates fags”— but religion is what causes them to hold these convictions.
It would be next to impossible to round up 30 psychopaths to carry out highly coordinated terrorist attacks if they didn't share the same reigious ideology--however perverse and distorted that ideology might be.