I read an interesting article which found that it wasn't necessarily a religious sect for many of its members. It was more of "if you can't beat 'em, join 'em" after the aftermath of Middle East turmoil after post 9-11 military operations by the USA and others. Give it a read. It made a lot of sense.

http://www.thenation.com/article/what-i-discovered-from-inte...