Gixer,
I don't think we can safely write off terrorists as just a bunch of murderous, brainless, religious fanatics. Indeed, they have a political agenda with several goals.
1. The expulsion of western powers from the Middle East.
2. The overthrow of Middle Eastern governments with ties to western nations.
3. The subjugation under Islamic theocracies of the rest of the nations of the world.
They firmly believe that, given enough time and money and patience, that they can achieve all three.