Okay this is an ACTUAL Conspiracy Theory, like with credible evidence n shit nah shayim.
alright, so first we need to go back to JFK's presidency, so like the CIA, FBI, and a hand full of Senators, High ranking military officials and some local government peoples all in on this plan to have the Cubans (fidel castro) cause a Terrorist attack on US soil. It was called Operation Northwoods luckily the President at the time refused this and had each person involved in the planning of this case removed from position and or sent to court over it while the ones who just knew about it were not fined (the elected senators).
Prior to 9/11 the Homeland Security Act was passed which was to assure safety of American Citizens from easy Terrorist attacks (such as mailing people Anthrax spores). It is highly believable President W Bush was aware of this and is the reason he acted the way he did and declared war on Terrorism and made a clear distinction between them and us. Keep in mind Operation Northwoods happen in 1962, and in the 1940s we were capturing US Japanese citizens to make sure they would not attack us from within. Just as we now have majority of states refusing syrian refugees because we want to assure there is no terrorist attack on our self's. Also never forget FDR's famous quote "There is nothing to fear but fear it's self" and Ben franklin's famous "Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety".