Because the FBI gave the terrorists all the training, weapons, and about $2bn in cold hard cash money that lead to them being able to commit the act. Because "jet fuel doesn't melt steel beams", although it does weaken steel beams. Because engineering and demolition experts came out and said the whole thing seemed coordinated exactly in the way in which they coordinate tear-downs for a living. Because the terrorists who on the same day planned to blow up the George Washington Bridge got sent home on a plane and were never spoken about publicly again. Because it was obvious Saidi Arabia had a hand in it, which later became confirmed fact, and we're buddy buddy with Saudi, so somebody had to have known something was going to happen but didn't sufficiently try to stop it on our side of the water. Because the Bin Laden family and the Bush family have a weird amount of connections. Be cause conspiracy theory culture was seen as more typical/harmless, and less of a thing for Nazi terrorists like today. Because the FBI had Bin Laden dead to rights in 1998 and had a bedside conversation with him instead of taking the opportunity to kill him while he was on dialysis. Because the 40 years that preceded 9/11 were lousy with proven incidence where our leadership, specifically the FBI & CIA in conjunction with corrupted presidents, in which American citizens were coerced, sabotaged, drugged, tortured, and killed, and all the leaders had to say about it was ‘whoopsy doopsy, so sowwy’