You guys are aware that these are all bribe related right? When you start an illegal casino and reach to 25+ people just jailed, god knows how many other people who gambled there, that means you have been around for a while. And you think Police never heard of it? They of course heard of it, they went there in civil clothes, asked to meet the owner, then talked with them about a good bribe to let them continue their operations, when the bribing finally ended or there was a dispute over how much it was, that resulted with the bust.
This happens in every nation, this happens quite frequently, there are illegal casinos all around the world right now, wherever you are, whichever nation or city, know that there is at least one place that allows gambling, even if it is small that is still true that it is allowed and nobody does anything about it.
What you describe is incredibly common and as you state it happens everywhere, this is why this is called organized crime, there are crimes that do not require the cooperation of the police but there are other crimes that are impossible to hide and the people behind those operations require the cooperation of the police and politicians to keep going on, it is also possible there was a change in the government and the reason they got caught was to spite the previous administration or that the person now in command of the police is not corrupt.