Yes. Similarly, Pakistani intelligence knew where Bin Laden was. Oh wait, SOME Pakistani intelligence knew. The issue we're seeing is internecine conflict and a lack of effective governance. Saying the hijackers were Saudis so therefore the entire House of Saud is liable is reductive at best.
I'm not defending said House, but OTOH blaming the most public power base for everything associated with the country ignores the fact that they don't have control over their own power bases (much like Pakistan, a total s-hole that I can't wait until we're disengaged from).