Not sure why any player in the top 20 would choose to match fix, surely they are earning enough already? Or is it some other factor?
Except players are not alone in the world. Family, relatives, friends, secret lovers. Who knows? Everyone wants a piece.
In many of the "match fixing scandals" both in eastern europe, in italian football etc it's been everything from a trusted friend of the girlfriend to business partners to actual illegal match fixing organsations (even from distant regions in Asia)
Only the most stupid player would leave a paper trail to himself and also use the money for himself. That would show. Match-fixing is much bigger issue where the actual player often is used as a tool, often pressured by friends/relatives/business partners/criminal organsations
Maybe in the low level circuit could you find some player acting almost entirely by himself. That's also the idiots that will get caught and easily proven guilty too