I’m not sure you’ve illustrated that it’s actually a bad thing for Lemmy to fragment naturally. That’s almost a certainty due to the nature of it. If Nazis started a server, which I have no doubt that they will, it will almost instantly be fragmented off, for example.

Lemmy isn’t inherently better with bigger user counts, part of the core idea is actually to have numerous smaller communities. The internet was plenty healthy before everyone all used the same platforms.