CIA management prevented this information from being disseminated by FBI agents posted inside "Alec Station", the CIA's Bin Laden group, several times, and they later lied about doing so. All this according to, among other extremely mainstream sources (in addition to the documentary record), Richard Clarke, who would know -- he was the Federal "Terrorism Czar" on 9/11 and has been fuming pissed about this since he found [1][2]. You don't need to be a whack job, a conspiracist, to be angry and mystified by this.
In many instances like this one, cursory investigation into claims of intelligence community "mistakes" or "incompetence" in these matters gives the lie to claims that these institutions somehow "dropped the ball" or "got it wrong" on 9/11, and are thus not to blame (either partly or fully) for the attacks. It's impossible to square such claims with a lot of the official paper trail. One can reasonably conclude that some of this stuff was not accidental. We hire these people to lie - why should we ever assume they're not?
(The best part? Many of the people involved in the events I describe were promoted in the years post-9/11!)
[1] https://abcnews.go.com/International/28-pages-questions-alle...