Don't know if it's $2 billion, but what they put on their website as of 2018-19 is less than that.
Where Does the Money Go? - NCAA.org
According to them, only $44.8M is going to administration/overhead at the NCAA. If this is true, they distribute the money to conferences/schools, other funds.
To the question of tampering, they literally have no way of proving it if they just keep one level of separation between the player and other program. If it's a friend of the family or someone in the player's circle that reaches out to the prospective school and has the conversation, there is not much there. And the NCAA has no ability to subpoena records from the school unless they have reason to believe a violation occurred. All Hunter or any player has to do is say any contact came after they entered their name in the portal and it's done.
With Frederick, of course someone close to him had assurances that Kentucky was an option when he transferred. And I'm not saying it's bad or that Fran should have done anything about it. It is what it is.