GitHub probably doesn't want to be seen hosting that shit because they're a company with business agreements and other businesses tend to start side-eyeing you and leaving you for competitors if you don't take action when people report racist stuff to you. (Usually because not cleaning that stuff up tends to be indicative of worse problems not being actioned on). GitHub in specific has a pretty nasty skeleton in the closet that they would really rather not have attention drawn to (their ICE contract, which has cost them several other contracts and has typically cost them about a third of their workforce every time it gets renewed), so they tend to be far more proactive in cleaning up that sort of thing.
Their TOS probably has a line forbidding this sort of mod from being uploaded and someone probably just filed a report to GitHub about it breaking their TOS or someone from their T&S team happened to find it while checking up on Automatics repositories.
As for the OK sign thing; that was a case of "4chan sliced a bunch of older pictures together of Trump and his ilk making an OK-sign" (which yeah, it's a common hand gesture, wow). The kinda strange thing is that it resulted in a sort of self-perpetuating effect; you had in part the media falling for the prank, but at the same time, those very same Trump supporters started doing the OK-hand deliberately to indicate what political "team" they belonged on.
It fell out of favor with those Trump supporters after a bit (because y'know, it was just a trend and trends defined solely by "trolling the libs" don't tend to last; eventually "the libs" catch on and they need something new).
Basically doing something ironically can make the people whose behavior you're emulating think they're in good company. Unless you take it to straight up absurdist levels (no Nazi will ever use Springtime for Hitler as propaganda), that will always happen.
Stuff like being clear about it being made to mock (as with Poes Law, which suggests things like the /s sarcasm marker) or extreme absurdity (Springtime) helps avoid that.
Ridiculous.
It's just when you compare the activity stats of the "black skin colors only" and "white skin colors only" mods on various modding platforms for all sorts of games, the "white skin colors only" mods have far more activity and downloads (although still nothing compared to y'know, shit most people actually care about like total conversion mods and the like), which tends to be pretty indicative of where the actual attention of the people who are into those sorts of mods tend to lie.
The "black skin colors only" mods pretty much only exist to create a more defensible position (the motte) for something that's blatantly unreasonable (having only the "white skin colors only" mods) (the bailey).
By looking at the activity, it reveals that this motte and bailey tactic is the blatantly flimsy bad faith defense it actually is.
All contained basically the same few lines of code that skew the number distribution for the "RandomMelanin" method in the game.
All three are still available on the Steam workshop, although it seems like the functionality of all 3 mods was merged into the "White only" mod, which now provides a slider that lets you select the range instead of hardcoding it, and that is the only source code that remained on their github. This is the only mod of the three that was actively updated for new versions of the game so that has an impact on the statistics as well.
This is mod as in modification, not as in moderator.
Its problematic. Maybe racist. But whitewashing?
The RimWorld mods aren't whitewashing, they're just problematic and when you take in the broader context of the history of these sorts of mods (not to mention the history of these RimWorld mods on the Steam workshop, as another commenter pointed out, they started with the all white mod and only uploaded the all black and all yellow mods later), are pretty clearly racist.
If you're not familiar, these sorts of mods are near universally made for racist dogwhistling; they're the "barely passable but not really" version of mods that would straight up whitewash non-white characters. The entire debacle started a couple of years ago iirc with the game Stardew Valley, which has non-randomized unique characters and someone made a mod to iirc whitewash the black characters that the game has (straight up just respriting them to look white).
The mod was pulled from both Steam and Nexus if I recall, and a few weeks later you saw these sorts of "one skin color only" mods appear in games with a heavy focus on randomized character creation (the uploaders of these mods also usually try to say it's not racist by uploading multiple variations such as a mod that disables all white skin colors; this is just flimsy excuses, which becomes apparent when you look at the activity stats for these mods). Modding sites aren't very reliable on taking action on them, so it's the loophole used to still get away with doing racist shit.