r/worldpolitics gradually became overtaken by US politics since Reddit is so dominated by US users. This displeased international users, as r/politics was already US-centric politics, and so r/worldpolitics had been seen as a place to discuss rest of world politics.
The head mod did not agree, and after a couple of years of the sub being basically unmoderated and 90% US politics, and generating user complaints as a result, threw a tantrum and said anything goes, and posted a load of anime porn.
Since the subreddit named world politics was now full of anime porn, and a little inspired by the subreddit r/marijuanaenthusiasts (the subreddit about Botany, since r/trees was taken by the weed people), a bunch of users decided to create a subreddit called r/anime_titties for discussing non-US politics.
(I'm unfamiliar with this.)