Its a bit of a mix as best i can tell.

Those that are recruited in "the west" are younger people straddling two cultures. The one of their immigrant parents, and that of the culture of the community they grow up in. Over time the stress of this life makes them lash out and open for recruitment.

Those from "the east" see their way of life encroached by "westernization" just as much as certain right wing groups in "the west" fret about "islamization". And over time the fear and frustration grows until they become violent.

The original Al-Qaida (every major member is now dead) which planned 9/11 actually didn't feel left behind at all. They were trying to fight change and westernization. I think that most of the current batch of terrorists, however, are just a bunch of primitive drug addicted machos who want to blow things up (and I'm serious about that, go read the Wikipedia articles on the people who have made attacks in Europe lately).

> The original Al-Qaida (every major member is now dead) which planned 9/11 actually didn't feel left behind at all. They were trying to fight change and westernization.

Go read the Wikipedia article about 9/11, they were fighting against the US attacks on Muslims, their influence on local politics, and their support of Israel. Why do people think it takes more than that?

Yes, they didn't like attacks, but "their influence on local politics" goes right into the "change" that I was mentioning that Al-Qaida was fighting against.

Edit: Please try not to tell people to "go read" it comes across as combative. Especially since I have read that article.

I was echoing your use of "go read."

Saying that's change is misleading. It's foreign control they're opposed to, and that has been normal for over a century.