You didn't get it. The film tells the story of how bookmakers are robbed with the help of fixed matches.
If bookmakers knew about fixed matches, they would definitely not accept bets on this match.
Just use Google or YouTube to watch the trailer!
The problem is that most ordinary gamblers like us have no information about rigged matches, or even if we know, we do not know who is going to win. Some bookies who are operating on a larger scale, they may have the knowledge of who is going to win and this can lead them making a lot of money in those matches.
The bet industry isn't fair, there are match fixing, rigged matches and all such stuff going on and big players are utilizing this to make more and more money.