This and God knows how many matches get fixed but pass through the public eyes without notice. Where there is money involved there is always chance for fraud.
This might be correct especially if you are doing this on a corrupt country, and probably some government official are making money here as well.
Fraud is everywhere, hard to tell if the game is fixed or not because the players can also be part of it. Sports betting are easy to fraud, if there's a huge money in the table. The mafia knows where to make money and with that, Brazil sports might be one of their favorite spot to do this. You're lucky if you are able to get a signal for a fixed matches, its not easy to have that signal though and no guarantee for if its true or not.
Match fixing or sports betting fraud is a big crime and unfortunately, the real beneficiaries for these are the national players and maybe the government is also involved in fraud of such a big level.
I will try to give you an example and you will see how big this game is. Let's suppose a Strong Team has a match with a very weak team and it is certain that a strong team will win. Almost 90% will bet on the strong team. Now the Strong team decided to fix the match, lose it, and before the match, they place a million dollars bet on the weak team (the odds are also high for weak teams).
The strong team loses the match, lose the match winning money but won 100 times more in the bet. The government can also involve in this if they decide to inject even more capital in this fixed match bet.