Unfortunately, there is a factual foundation for the FBI and CIA not sharing information back then.
Finished The Looming Tower and it left me feeling drained. I'll definitely investigate the Barnford books. If the show is accurately sourced it essentially tells us the CIA knew Al Qaeda operatives were in the US in March 2000 and had Intel that at least two of them were taking flight training, but take-offs only. And not only did they not tell the FBI, they actively withheld it and refused to divulge it when the FBI realised there was activity but some info was missing.
Not pleasant, but one of the shows of the year. Gripping and horrifying.