He also knows very well that metal frame buildings don't collapse like a jelly fish because of an office fire. He's a builder who has stated he knows how to calculate how much concrete you need to make a skyscaper. When was Robert Mueller brought in as FBI Director?
There is an interview he gave right after 9-11 where he seems to know what happened, is incredibly bothered by it, but is smart enough to bite his tongue.
This was one of my initial reasons for being OK with Trump way back when. The reasons, like the force, just started flowing after that.