Don't be surprised and the government will always use that excuse and it's also commonly used by countries that block online gambling sites.
My guess is actually not money laundering that is their focus but their inability to collect taxes from online gambling activities the reason behind this blocking.
Which usually happens when the government does not benefit from the activities carried out by its people, the steps taken are prohibiting, blocking and so on.
Maybe you are right that they are only using the ban as an excuse to hide the shady things that they do. They think some people are going to be happy once they ban gambling because those people are also anti with it. They think gambling is bad and it destroys lives but we aren't agreeing with that. Only the responsible gamblers will understand what is the true benefits of gambling.
Online gambling especially non crypto are regulated so they can be able to get tax from it unless if they don't want it anymore because their economy are doing well already. The move isn't about money laundering because laundering can happen on many ways, exchanges for instance but they didn't say that they banned it.
High likely it is owed to the fact that they don't have the control over those sites and so they can't tax those casinos accordingly. But if those sites are regulated under their government, I believe they won't have any problem. But these gamblers will always find a way how to gamble and find new casinos to play with. We are in the digital age where you can bypass the government's banning protocols.