They seem to be specialized forks though, not actual recreations of the entire Wikipedia. We should have like an actual Mediawiki instance that forks the current Wikipedia content and maybe also leeches contributions off of it for some time to keep it up to date.

Who's this "we" exactly? Who's going to host the infrastructure? I don't think it would be so trivial to "just make our own."

There are various reasons to avoid a fork. Having the resources to maintain such a site, spreading resources thin, and moving over or rebuilding a community of trusted editors are among them.

That said, I am one of the people who downloaded a copy of Wikipedia. It wasn't with the intent of working it. Rather, it was to wait out any political strife (since that is bound to happen with such a large and diverse audience).