Hoover took over a corrupt FBI, that was corrupt from the beginning. Hoover 'libraried" everything, then turned that against Congress (black mail, if you will)
Hoover said there is "No such thing as Organized Crime". The Federal Bureau of Narcotics broke that myth with Joe Valachi. seems Sam Giancana had photos of J.edger in bed with his #2, yup, just like the movie showed. So their HQ is named the Hoover Building (LOL).
After Kennedy was assassinated, the FIBs said "We are in charge here." 10 Days after JFK was shot a letter (believed from an FBI Agent) arrived at the SS. (Check internet for something I heard on a relative timely basis.) They could not find an reason for the pristine bullet on the gurney; lost Kennedy's Brain and took years to announce there was a 4th shot at Dealey Plaza. (Where from and by whom?) The first rule of assassination is "kill the assassin",Ruby did.
Bush after 9-11 Cooperate with other agencies. Lasted 3 months.
Whitey Bulger - convicted after the FBI was replaced by a special Task Force. While their informant, killed 2 and put 4 in prison (Mueller was Dir FIB then) based on a frame by Bulger to eliminate competition.
Unable to find CIA mole Aimes.
Then we can go on and on. Trump Frame up, false FISA warrant, Hillary non prosecution; Sedition; and so on. As far as I know there were only 2 FIB Directors of any note before the current one.