They had political and religous motivation. They did not represent Muslims. The motives for the attacks include the presence of the U.S. in Saudi Arabia,the support of Israel by the U.S., and the sanctions against Iraq. They acted on their own.
and dont forget the "perversions in Hollywood, and Bill Clintons infidelity"
those were included
also the fact the US wasnt under Sharia law
they had quite a laundry list
they still insisted it was for Islam even if they were the only ones to believe that, it is still a fact