The new rule didn't come out of left field. Google banned crypto-mining extensions from the Chrome Web Store back in April due to "malicious software developers who attempt to abuse the platform at the expense of users." We'll bet that's also why the tech giant has decided to implement the same rule for Google Play.
The store will now also ban any app made to appeal to children but contain prohibited adult themes, most likely to prevent "Elsagate" apps from multiplying any further. If you'll recall, one of the issues YouTube is grappling with is the spread of disturbing and violent videos masquerading as kids' shows. Google Play has the same problem -- while it's probably not as bad for the platform as it is for YouTube, it's also been hosting a bunch of kids' application that actually contain creepy images and videos.
In addition to those two new rules, Google Play will now also ban any app that sells explosives, firearms and ammunition. Plus, it's taking steps towards getting rid of low-quality, low-effort applications. Apps that rip off others without adding anything original or anything of value, as well as multiple applications with "similar content and user experience" created by the same developer will now get the boot. The Play Store will also kick out apps primarily made to serve ads and those that intend to mislead users by pretending to be something else entirely.