No government in the history of mankind has ever been capable of keeping a secret.
Even the military has a tough time of it.
The American people just like to think they're invincible - that a few terrorists sitting around talking could come up with a way to hurt them, and pull it off without the ever-vigilant, all-pervasive security organizations catching them in the act. It's always got to be some huge, sprawling conspiracy involving thousands of intricate details and evil people, and the US Government betraying the people. It can never just be a bunch of guys who didn't like them getting lucky.
Anyone who has ever seen a ****ing brick-shed collapse knows that the Twin Towers were not a controlled detonation. They didn't collapse or explode, they ****ing crumbled.
But, y'know, even if the CIA did explode them - what the **** else were they gonna do? Just let two huge pillars of concrete topple over onto the rest of the city? Grow up.
As for the Pentagon, I actually do think there was something fishy going on there. Like a missile. C'z it sounds a lot better going "Oh yeah, there was a third plane that hit the Pentagon", than telling a room full of reporters "Plane? No, they smuggled a long-range tactical missile into the country, set it up and launched it at the US military HQ from 50 miles away."