Steam has removed a large clutch of games of various genres which all seem to have one thing in common: they were low effort shovelware. That might seem a slightly mean designation, but we've all seen the type of thing that this ban wave targeted. Extremely basic asset-flipped titles with popular words in the name, such as Zombie Defense TD or Play Football, out there just to try and make a few bucks from the unwary.
Ever since Valve opened up Steam this has and will continue to be a problem, the inevitable downside of what is inarguably an otherwise good policy. Steam's biggest issue these days, for both developers and players, is discoverability, and the sheer mass of shovelware on there is a big part of that. While this ban wave appears to have removed 90 games total (per SteamDb's tracking of removed apps, available via Discord), that's still a drop in the ocean.
Not all of these titles were removed for the same reason. I doubt 3D Pacman was an official Bandai Namco title (kind of amazing it got on there in the first place) and Dong Nguyen would no doubt be surprised that Flappy Bird was apparently available too.
As well as the games themselves, most of the developer accounts involved also seem to have been banned. Which is unambiguously good for the wider ecosystem. Obviously everyone has to start somewhere, and developers learning their trade often make games using easily available assets and in an established style. Most developers don't then go on to try and flog their juvenilia though, and the veneer of legitimacy Steam adds to even the dodgiest looking title means that no doubt players have been suckered into buying titles like these in the past.
There's clearly something going on behind-the-scenes at Steam right now. It had been a while since the last ban wave like this, and it follows hot on the heels of Valve beginning to pay a much closer eye to games with AI-created assets on Steam (this is not, as widely reported, an outright ban). There was a big front-facing change recently, too, with lots of new functionality (some of which was exploited by ingenious Counter-Strike players for ez wins).