The cognitive dissonance come from the fact that you can't really think it was a large number of people inside the Bush government, because these people were not selected for psychopathology in advance. If it was an inside job, it had to have been a very small number of people, perhaps even only one person, working completely alone.
In order to pull off 9/11, you absolutely need other people to work for you. So they need to do it without knowing what it is that they are doing. They way to arrange this is by ordering a bunch of coordinated drills. You make four drills:
Put drones in the sky to practice intercepting airliners.
Simulate hijacking on actual commercial planes
Confusing radar blips, software glitches
Flight-simulate flying planes into the World Trade Center and Pentagon.
On the day of the attack, you use drill 2 to turn off the transponders, you use drill 3 to switch the position of the planes with drones, and you use drill 4 to get professional pilots to pilot the drones into the targets.
While it's going on, you can transfer passengers to flight 93. At the end of the attack, you order flight 93 shot down, and that's it. You've got the attack.
It requires this combination of drills. You will only have about 3 people who will know what happened, the 3 pilots who were simulating flying into the towers and the Pentagon--- they will quickly realize what they did. But you keep them quiet.
The rest of the people just notice that there was a freaky coincidence--- that they were having drills about the thing at the same time the thing was happening.