Trademarks
I don’t know what the rules are in cowboy land but certainly in the UK, a trademark cannot remain registered as such of it is not in use. This is to stop someone just squatting on a trademark to stop it being used by someone else (which sounds suspiciously like what Musk is trying to do)
Clearly Xitter no longer wish to use the twitter trademark, and I’m not convinced just having the twitter domain name counts as “use” for these purposes if it’s not being actively marketed as such.
If the trademark was never “registered” then I think it’s fair game anyway - I’m sure someone will correct me if I’m wrong