Good afternoon ! I'm from Ukraine. To be honest, I have not met people who would bet such huge (for our country) sums of money on matches of the lower leagues of Finland. Not everyone can bet $1,000 on the European Championship final. Either this guy is a millionaire and doesn't care about money, or this is a dirty deal. I often saw a message offering to buy accounts. In our country, match-fixing scandals also often occur. This is especially true for youth teams. This is how the U19 team from the youth championship was punished 2 years ago. Their players played fixed matches. And there are many more similar stories. I'm just too lazy to look for them
Your points make a lot of sense, but this doesn't 100% prove that the gambler in question cheated though which is why there was always a chance that they robbed him off his big winnings.
Also, if they have issues with such low level leagues, they never should have offered them in the first place. They are the only proper crypto betting exchange currently which is why it's sad to see them behave in this manner.