Isn't 6 months enough for an investigation to commence?
Apparently not. But that's not surprising: match fixing is a crime, which means there's a criminal investigation, which means the government is involved. Or multiple governments. I can imagine this isn't a high priority to them, and from what I've seen in the news about (different) crimes, it can easily take a few years to bring the bad guys to justice.
Whatever job you do, would you justify your employer holding your money for 1 year because they "suspect" some match fixing? If they have any reasons to believe the game was rigged they should post the proof and if not then allow me to withdraw.
It's easy to come and look like a saint when others are struggling to get money from a giant casino scamming them but when it will happen with you, maybe you realize how it feels for others to come and say "yeah it's fine, investigations can take decades and casino will pass the funds to your grandchildren, why are you troubling them"