If the last several years have taught us anything, it's that the one thing people will pay through the nose for is the chance to see rich, entitled assholes getting their comeuppance in humiliating displays. I mean that's basically the only reason to keep watching Food Wars after you grow desensitized to the fan service.
But no anime on the market right now is better at portraying the upper class as haughty nitwits who are fun to bring down a peg than Kakegurui. Kakegurui is, primarily, a gambling anime, centering around a girl who loves to play seemingly rigged games of chance against her rich classmates, due to her love of the thrill such games provide. Though if you ask any Kakegurui fan what they love about the show, the gambling itself will likely be an afterthought. The way it handles its games pales in comparison to much better gambling shows like the thriller masterpiece Kaiji: Ultimate Survivor, but what makes the show so entertaining despite that is the character interactions and of course, that pure thrill of seeing entitled brats being put in their place.
It's not the most complex formula for a hit anime out there, but god damn does it feel good to watch.