I don't believe that at all. I believe they attacked to kill infidels and frighten the West. I believe that in so doing, they succeeded. But at the most basic level, they wanted to fly planes into buildings, thereby killing people and destroying said buildings, and mission accomplished there. Now, on the larger scale, I agree that terrorism has a pretty much 100% failure rate, in that it tends to actually strengthen the resolve of the people being "terrorized", at least in so far as fighting terrorists are concerned. As far as complex reasons, to quote a line from TWW, "your ridiculous search for rational reasons for why someone straps a bomb to their chest is ridiculous."