I would think that rebranding CentOS as Rocky is a rather trivial process of replatforming all the codebase and replacing any “Centos” with “Rocky”.
In short, forking it is easy, but keep it attractive is not.
I mean, if you think about it, all that's really needed is for a "s/CentOS/Rocky/g" over all of the repositories. Then, the other 99% of the project is just waiting for the packages to rebuild and get sync'd on all of the mirrors that they could just will into existence with their minds.
Really, though, let's be honest here: If they weren't spending so much time writing up press releases and commenting on issues on GitHub, they probably could've already basically been done, the new package repositories could've been published and mirrored, and half of the CentOS 8 boxes out there could've already been migrated over.
<sigh>
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EDIT: To be clear, I am not serious. I thought the question I was replying to was completely f##king absurd but chose to respond with sarcasm (it seemed less likely to result in a warning from @dang than my initial reply).
You would also need I said if infrastructure servers that can scale to a large number of users for Yum/RPMs, etc.
Then you also need a set of servers for issue tracking and a way to break it out per package.
I wouldn't imagine that it is anything which can't be done, it just seems like there's a lot of little pieces that you would need to set up, and infrastructure you need to run.
Not saying all of the above is trivial but I'd think the code to do it literally exists and is itself open source.