In the perspective of Wrestling, it's pretty easy to fix matches, since you have mainly two people (with surprise guest appearances in some parts of the show) duking it out. We even see people in suits give "words of advice" to the wrestlers, aka "here's the plan". Essentially, "plot twists" are part of the show and they get money from this, even if some of the more blissful audience members do not know.
How in the world do you fix a 20-man-each match of skill, where none of the players are actors and 12 high-definition cameras are pointed at the arena at all times? We'd be able to catch severe acts of amateurism on replays.