For example, just look at 1xbit. They have a valid license, but it doesn't matter since they are proven scammers who cannot be tracked down easily.
It's the massive marketing they do. I think in online there are many places they are advertising their banners. They have sponsored big events, even in the mainstream media they have ads displaying all the time.
Casinos that I trust are: Metawin, Bitsler, Crypto.Games, Sportsbet, Livecasino, Bitcasino and some others, you can do your research on them by the way.
Stake, Duelbits are in my list too.