I think you're missing the fact that everyone knows. He just got reliable data from a natural experiment, which makes the chancellor can't just look away any longer.
People for sure have always cheated in these take home exams. This has to have been to protect rich kids with parents who give money to the university. It's insane to learn how many fancy universities have garbage blatantly unmeritocratic evaluation systems like this
That is true, and it was always a bad idea. But hey, economics. If economists should be aware of anything, it's that university financing in large parts of the world have perverse incentives.