I suspect the reason why the full story isn't being told here is because the creators of Lix don't want the project to be seen as purely some "left wing" fork. I don't blame them, especially considering Lix has far more merit than merely "Nix's leadership sucks." Regardless, I'll see if I can give you an overview:

Basically, NixOS's leadership has been seen for a long while as bureaucratic and sloooow even when it comes to core things like UX changes in Nix itself. When it comes to social issues, they have been dragging their heels even more. A lot of discontent has been brewing for years but the most notable conflicts have been when NixOS's leadership accepted funding from Anduril to fund NixCon 2023. Anduril was then dropped as a sponsor, but NixCon North America 2024 again got sponsored by Anduril. Anduril, in case you didn't know, is part of the military industrial complex, and is run by Palmer Luckey, a noted Israel supporter in the ongoing genocide against Palestine.

NixCon getting Anduril sponsorship again ticked off a lot of people. This petition was then opposed by a particularly loud and irritating chunk of the community, including Jon Ringer, a (now former) release manager for NixOS, and most notably, an Anduril employee. Jon maintains that his Anduril employment was irrelevant to his work on Nix, which may very well have been true; up until the point where he started going on rants about Nix becoming "political" in discussions about the sponsorship. He stifled a ton of discussion around this issue, and NixCon went ahead with the Anduril sponsorship. Now that he has been "doxxed" (his employment details were public on LinkedIn, he uses this term to drum up more support for himself dishonestly) he has gone full mask off, and now spends time on the grifter's ~~shithole~~ paradise r/NixOS to complain about how the "woke left" is supposedly trying to infiltrate Nix's leadership and "take over the project" (partly because of the Anduril sponsorship response, partly because of this one RFC where someone dared to advocate for minority representation).

People have been advocating for leadership change to at least try and get NixOS's leadership to do more, but apart from Eelco (the BDFL) stepping down there hasn't been a whole lot that's changed. After reading a lot of these discussions and seeing just how inactive some of this moderating has been (and the fact that when a mod does try to clean up the forums, the grifters cry that the mods are being "political" or whatever the fuck), I'm personally throwing my whole weight behind Lix, because I appreciate project leadership that aims to have a safe community. That, and I also like a project that isn't scared of breaking experimental features.