He was whistleblowing on Deustche bank taking advantage of their shareholders, and in turn is being paid out of a fine that they had to pay (which, of course, comes from the shareholders themselves not the accused execs) so it's a bit of a perverse incentive for him. The rest of us can stand jaw-dropped at turning down a massive sum of money, but bravo to him for pointing this out with his (seemingly selfless) action here.
Maybe his comment “I will not join the looting of the very people I was hired to protect.” explains that.
Right, but didn't the bank still have to pay the money?
If the bank didn't have to pay the fine, the money would have went to the shareholders. But it was the shareholders who were being defrauded in the first place that made the guy become a whistle blower.
The crooked executives got their bonuses and didn't have to pay a fine.