What did they actually do to kill it?

The 2 quotes just say "they killed it", but the way I read it having followed most linux stuff is just they are finally happy that they were able to "kill X.Org" in RHEL by being able to provide an alternative that they are able to actually improve upon.

And metux was banned from my knowledge after multiple times pushing uncompilable and breaking changes to the actual X.Org repo, which later needed to be reverted and just being stubborn as all hell to work with. Recently even Artix had to drop XLibre support for causing too many issues[0] to put it lightly.

[0]: https://artixlinux.org/news.php#XLibre_support_discontinued