I was thankfully notified ahead of time about the developing story here, and it looks like the mediaTM hasn't showed up to report because it's a very small story, actually hard to believe this is over a week old and NO ONE had much to say at the time the news dropped.
SFW Content, NSFW Blog, links head to mostly SFW sources.
Internet persona and creator with quite the history (not all of it good, mind you) Tom Fulp announced in a post on the Newgrounds Forum (click here) ~11 days ago that Nintendo was mass flagging the adult works in the Nintendo-character tags hosted on Newgrounds. Newgrounds is ANCIENT, there is probably at least 15 years of content Nintendo's lawyers had to detect and DMCA in some capacity, possibly thousands upon thousands of works. Talk about being aggressive, eh?
Copyright Law in Japan (Wikipedia) is the factor here, like their attacks on creators via Youtube and Patreon before it, Nintendo hoards absolute authority over everything internationally, Newgrounds included. History has shown Japanese Copyright law makes no provision for Fair Uses, not even in the form of targeted Parody. Parody itself doesn't even matter, they basically just have to prove you are making money in some relation to the IP's involvement by reference. This famously caused a pokemon porn purge on Patreon (here's a journal on Furaffinity.net in 2019), and Youtube once had the "Nintendo Creator" program (Kotaku, 2018) which harshly restricted your ability to post clips of Nintendo games being played. Now-a-days they just have a "policy" (Gamerant, 2023), which still does basically the same thing with less involvement from them.
As mentioned, Nintendo has some history here and is notoriously finicky about if or if not they're going to risk market and brand on engaging in even mildly mature products. Doom 2016 and Skyrim arriving on Switch was actually pretty significant in the company's history, with a sparingly meager selection of 17+ audience works in the library. In looking for coverage on this new story, I found instead a 4 year old article about a similar takedown that involved an adult/erotic princess peach game being struck after 8 years of life. You can read that one right here (MyNintendoNews, 2020).