I think you should consider taking a upper-level course in terrorism/counter-terrorism or something similar at Baylor, if they offer such a course. It might give you some insight into how difficult it really is to figure out what is going to happen, before it happens.
Although it is tempting to say, post hoc, that everyone should have predicted and prevent 9/11 (and, correspondingly, their failure to do so indicates something odd), it doesn't match up with reality. In real life, the act of preventing terrorism is extremely difficult and time-consuming. Terrorists tend to operate on the fringes in small groups, lacking the kind of infrastructure that can be readily observed by intelligence agencies in order to get a clear picture of what's going on.
It's difficult to pick out the significant stuff unless you get lucky and have good intel.
9/11 may have been big, but it really wasn't that complex. It exploited several major weaknesses in the US system, which is something many terrorists are painfully good at. After the fact, it's easy to say "yeah, we probably should've detained this guy" and all, but at the time it wasn't so obvious.