I don't think they are as intimately linked as they once were, back in the day, most gambling houses were controlled by criminal organizations such as the Mafia, which meant that mostly criminals and guys from the underworld would be involved. However, since it has been legalized, there is no longer any criminal association, it is as clean as can be in most cases, and even most crypto casinos are licensed nowadays.
They used to be intimately linked in the past (just wanted to use that word of yours), but in reality times have changed.
Yeah, there may be some casinos that still tend to do some illegal shits and then you get to see some criminal activities revolving around them, but that certainly depends on whether gambling is legalized and regulated or not.
For now, in most countries, it has been legalized and of course, opening a casino now requires you to get a license as a business man, and it is only someone who would want to jeopardize that, which would end up screwing up with illegal and immoral activities around the casino.