Exactly, but I believe that those fixing matches secretly will definitely be caught some day because it will be revealed. I only love betting on big leagues because it is rare to fix matches since they are professionals and it's against the law, because it will kill the fun and quality of the competition.
Match fixing is always targeted at lower leagues where attention is not high and rewards are not as important or significant, so it appears to be a lucrative deal for the teams involved. They can even fix a correct score, which will be difficult to dictate because those leagues are not taken seriously because their primary function is to groom players.
This is why the majority of the match-fixing scandals that have received a lot of attention have come from major leagues, as all eyes are on these leagues to ensure professionalism and maintain the league's reputation. If match fixing is not closely monitored in these major leagues, the football community will not take the results seriously.