And some times, having the initiative to create such more specific communities could be a change factor for the growth of a social media. Also, with federation, not just the person can choose where to create the community on while not making it a walled garden as other sites would still have access to it, but also if a community for the given subject already exists but the user thinks he can do better, he/she can more easily do it with how expansive the “fediverse” is.
And if the user uses Mbin instances, he/she can even block posts that link to other domains, as often political posts link to news sites.