Honestly, I can still see a far gap between both companies, it's not a bad idea if Rainbet decides to adopt a strategy that an old casino used which favoured them, so they (Rainbet) decided to apply it too, that could be what just happened there and nothing more. I've seen that stake pushes their ads more than any other casino that I know, even more than rainbet does.
Yes, I totally agree with what you just said above regarding Rainbet Casino just adopting a working strategy that an older casino have used before and succeeded in its casino operation business across the globe. And for the fact that they both accepted to use the same strategy, doesn't make them been own by the same company. However, there is one thing which O.P said which I have personally noticed which these two casinos have in common, which is by aggressively promoting it's services through the use of clippers on the most popular social media platforms like Instagram, TikTok and YouTube. And they are commonly been promoted on Meme Instagram theme pages, which usually gets millions of views. And I'm pretty much sure that these promotions have really been effective by giving them these awareness they needed in getting the brand known globally.