It seems they don't play about this in some countries and I think that's how it should be. But if the gambling company is legit and doesn't scam people then there's absolutely nothing wrong with taking endorsement deals from gambling companies. In my country celebrities help to advertise scam casinos and this is actually the main problem and it's what must be corrected but no one cares to call them out
From what I understand, there was no scam accusation against the casinos but they are operating illegally in their country. By illegal it means they are operating without the necessary licenses and probably no documentation and no revenue to the government. The celebrities were arrested because their activities look like supporting that illegality, something the government see as unpatriotic and misleading to the general public. It's also important to note that as the casinos are operating illegally, it will be very difficult for the government to protect their citizens from losing money to them and in the case of the casino operators running away, there will be no way of getting them because they were not documented.
The case seems different though ot against the promoter's and the government, the celebrity was not arrested because of any failure in the part of service provision to customers but he get arrested for wrong influencing which is within the right of the government at some point to prevent illegal operations of casinos.