The original signers include members of the infrastructure and moderation teams. You can find about half of them on Mastodon. They’re all well-established community members who hold real responsibility and roles within the NixOS Foundation ecosystem.
Also note that Eelco isn’t “a maintainer” but the original author and designer, as well as a de facto founder of Determinate Systems. He’s a BDFL. Look at this like the other dethronings of former BDFLs in the D, Python, Perl, Rails, or Scala communities; there’s going to be lots of drama and possibly a fork.
You’re right. I incorrectly believed that hexa had signed based on their comments elsewhere, but I was wrong.