I'm not sure I see the benefit of this. The point that Wikipedia might eventually become corrupted is made moot by the permissive licensing of the information there. The main challenge of the Wiki format is with fact checking and ensuring quality, which is only made more complicated by having a federated platform.
ActivityPub is great for creating the social web. The added benefit of ActivityPub for non-social services is not obvious to me at all.
That said, it's a cool proof of concept, and I'm sure it can be useful for certain types of federated content management - I just don't see how it could ever make sense as a Wikipedia alternative.
Then again, why would a fan page want to open for contributions from outside of that fan page? Why would the Star Wars wiki federate edits with the Startrek wiki? On which page of the wiki would this make sense?
I guess you don't have to get it. I just mentioned that site as an example because it is kind of garbage, but it's useful for fans.
And the federation between fandoms would be like how different articles are connected on Wikipedia. For example, there are actors that had roles both in the Star Trek universe and the Star Wars universe.
Lots of those fan wikis just link to other websites. It's entirely possible to do that.
If you're on a Star Trek wiki, why would you want to go to a page that's almost exclusively talking about Star Wars information in relation to some actor other?
I was pointing out that the two fandoms are actually connected by some actors because the person I was responding to seemed to be unaware.
Maybe no one does this, but I've looked at character pages and clicked on actors' pages if I liked them and wanted to see what other work they've done.
The main reason people use Fandom in the first place is the free hosting. Whether you use MediaWiki or any other wiki software, paying for the server resources to host your own instance and taking the time to manage it is still a tall hurdle for many communities. There already are plenty of MediaWiki instances for specific interests that aren't affected by Fandom's problems.
Even so, federation tends to foster a culture of more self-hosting and less centralization, encouraging more people who have the means to host to do so, though I'm not sure how applicable that effect would be to wikis.