Steam has also been hosting numerous outright neo-Nazi groups for many years (PDF) and never really stepped up effectively against them. User reports and media attention has limited effect.
As a general rule, steam discussion boards for a game are moderated by whoever the developer assigns that power to, and steam user groups are moderated by the group owner or whoever they delegate that power to and Steam doesn’t particularly care so long as you aren’t doxing, openly coordinating harassment, or doing something explicitly illegal in the US.
That’s also the general tilt they’ve taken with what’s allowed on the store since they opened the floodgates - if it’s not illegal and it’s not going to get them sued, it’s probably allowed if properly tagged. Which is why you can find Sex With Hitler side by side with Super Lesbian Animal RPG.
Worst they do is block it from specific regions if the local government requests it - see that game where you essentially play as Hamas fighting against the IDF that they recently blocked from the UK, the one where the largest part of the game description is arguing that the game isn’t antisemitic hate speech just because the enemy are Jewish. The call to block it came after a new patch that apparently added a scenario based on the Oct 7 attack.
I mean the point of all rating systems in the US was fear of government regulation of content and having to fight that particular legal battle. It basically exists because moral busybodies were upset about Night Trap, Mortal Kombat and Doom.