I hardly ever see anyone say players are involved but when I put on my thinking cap of conspiracy, leaving things to the refs leaves too much to chance and can be obvious depending on the situation. The best way to rig games is to pay off the QBs. They control the ball for every offensive play. There's 2 people to split a pot between versus a 7-man ref crew. The less people who "know" the less chance it gets out. Plus, throwing a game is almost undetectable and can be written off as just having a crappy day. Two Cowboys examples I can think of was Neil O'Donnell during our last Super Bowl win and that game a few years back where Dak 'almost' threw a pick-6 to a Washington DB and then immediately ran the same exact play to the exact same side of the field and did throw one to seal the L.
If the conspiracy people say refs are human beings and thus corruptible, I don't know why players as the same human beings aren't as well. Why that's a bridge too far for the "theorists" is interesting to me. It's like they only want a conspiracy they can be on the wrong end of for victim's sake but can't stomach a league-wide one that doesn't make them "special (which they are, in a 'special' kind of way)." If you're gonna 'spiracy, at least choose the most logical path to it.