What do you mean he didn't know about it? He's a banking exec whistleblowing on tax evasion. The IRS bounty on recoveries is not exactly a secret. Even in the unlikely event that he himself wasn't aware of his prospects when he went in, you'd assume literally the very first thing any competent lawyer would have told him was "you stand to make a hundred million dollars if you go through with it".

The thing I like about the precedent? That banking executives need to be on their toes because all of their colleagues have an immense incentive to rat them out.