You don't necessarily need the complicity of Bin Laden, or that many people.
You just need your intelligence agencies to keep track of what he is doing and allow him to continue because the attack suits your purpose (e.g. finding an excuse to attack Iraq).
Re:Conspiracy: In Theory and Practice
by fighterpilot on Thursday July 01, 2021 @10:21AM
(#27699308)
That's a much more plausible version. It's still more complicated, though, and requires the complicity of many more people, and is therefore less likely to be true. There's also the rule of thumb that we shouldn't presume malice when incompetence fits.
Just because they're two unprecedented scenarios doesn't mean they're equally simple explanations.
Not only do you need the complicity of Bin Laden and his associates, you also need the complicity of many people within the US and you need them all to shut up about it and you need Bin Laden and his associates to lie about what really happened and you need to hide any trace of this from investigators. This is massively more complicated than the banal explanation that the small group of people who say they did it, actually did it.