Corrupt Sports? Every Sport has some of corruption going on.
I dont understand what you mean by "despite being the sport that should have the most random variation"
Low scoring games like soccer and hockey have a naturally higher chance at upsets. However, despite upsets being easier in soccer out of any other team sport, they have the least amount of parity. This is a class A example of a badly run league.
NBA should have the least amount of variation in their top teams, which it does for the sports that matter, but soccer has less parity and that's frankly embarrassing for soccer.