Is it true he denied the Mafia was a thing

It is more likely that Hoover denied the Mafia because he knew he could not take them down. The organization was too large, protected by politicians/local police, and well-organized (I did try to avoid the pun).

Before RICO laws were passed and later used, the Mafia was a hard nut to crack. Eliot Ness had to use the IRS to take down Capone. Even with RICO laws taking the Mafia down was time consuming.

Edgar was an ego-maniac. He liked to see his name in the media. Quick hits on in small-time independent bank-robbers got him that. Dillinger was small time when you analyze his career, but his charm made him headlines news. He was Hoover's plum.


The same with his pursuit of Communists. It made headlines and they were easy marks.

The Mafia may have known he was gay, but he didn't frighten them.

I am sure additional reasons exist, too.