Because he didn't traffic children.
If you look at the charges of Greenberg and that essentially nobody once ever referred to Gaetz as a suspect but rather "subject of" or "involved in" it becomes pretty clear what happened.
Greenberg was running a blackmail ring, or at least managing it, Matt Gaetz was the target of it. He started getting suspicious and went to the FBI.
Under no circumstance would the dems be running RFK if Biden wasn't in the picture. RFK has never been anybody within the party and Democratic voters don't like him that much, to say nothing of his discredited beliefs that are pulling more conservative voters to his campaign than liberal ones.
But we should look at why conservative voters are responding so well to him.