> The 9/11 hijackers were mostly on tourist visas from a place with almost no history of terror attacks:

Your source (correctly) says they were mostly from Saudi Arabia, which has a rather extensive history over several decades of terrorist attacks (both attacks in Saudi Arabia, and attackers outside of Saudi Arabia by Saudi nationals and/or with Saudi sponsors.) There is no sense in which Saudi Arabia is (or could be fairly described in 2001 as) "a place with almost no history of terror attacks."