It's a rigged game. If there's a bet that player X will foul player Y, without proper safeguards, player X can bet on himself and then intentionally player player Y. The actual harm is that by the rules of the betting, no one should know the outcome who could also bet on the game, so the losers are being robbed of their money.

In this particular context, it's also possible that there are illicit transfers of money without being immediately noticeable. Bribery could happen at the highest levels with it being very difficult to trace and prosecute.