From what I could gather, the main factor that led the community to this point is Anduril's involvement in the community. Anduril is a miltech company and a contractor of the USA DoD. It looks like they use Nix extensively to train ML models and deploy combat drones, and several of their employees have very close ties to the Nix community; Jon Ringer (an Anduril employee, who is mentioned several times in this document) has recently been a release manager for three versions of NixOS, and was nominated to become a release manager for the upcoming 24.05 release.
Anduril wanted to sponsor NixCon last year because of this deep involvement in the community. I was not there to see it, but from what I've seen lately, many members of the community were not happy about it. The sponsorship was eventually pulled, because the on-site video team for the conference (https://c3voc.de/) threatened to pull out on their own over this sponsorship.
From my understanding there has been no official decision taken over Anduril's sponsorship since last year's debacle. Many people in the community think that this is because Eelco Dolstra, the creator and de-facto BDFL of Nix, is currently employed by Determinate Systems, which is rumored to have a contract with Anduril.
Edit: I just want to make it clear that I don't agree with what is presented in this document. I just wanted to present an overview of what, from my perspective, happened up to this point.