Supposing there were actual "terrorists", they seem to have been a bunch of losers who were incapable of pulling a stunt such as the Pentagon maneuvers (by the way, how can a plane totally disappear into a structure and leave an opening narrower than the wingspan? That has me totally befuddled. Plus who has ever heard of plane crashes on land where the craft has totally disappeared? None before of after the four in one day!) If these guys actually existed, they were mere patsies (and I suspect the Pentagon and PA flights were missiles).
As far as I am aware, there is more evidence connecting the US and Israel to the 9/11 attack than the KSA, but it's more politically correct to go after the KSA than the US government and Israel.