And the interesting thing, IMO, was that he got tips on fixed races from FBI agents. He had to have known that the tips came from criminal sources, but he just ignored that part. He was a small-time bettor, anyway.
Hoover was a lifelong bachelor who shared his home with Clyde Tolson, his second-in-command. He's had several competent biographers, all of whom tried to check out rumors that he was gay. They weren't able to prove it--which doesn't mean he wasn't gay, just that they found no evidence to prove it. The dressed-in-drag photo is probably a fiction.