Demetri Kofinas is the host of the great podcast Hidden Forces. He's spent more time and thought than anyone else I know personally digging into still-unanswered questions about how 9/11 happened, how much Saudi government involvement there was, and whether the CIA may have had information that should have allowed the prevention of those devastating attacks.
Saudi Arabia & the CIA’s Actions Ahead of 9/11 | Bob Kerrey (hiddenforces.io)
What Really Happened on 9/11? | Ray Nowosielski & John Duffy (hiddenforces.io)