You are dodging the issue.
Between 9/13/01 and the invasion of Iraq the Administration could have quelled the rumor with truth. It didn't.
There was no rumor. Only a decade of experience with Saddam Hussein.
You seem to start with the assumption that if Saddam was involved in 9/11, there would be evidence of this involvement and we would find it. I think the opposite assumption would be a safer bet.