The first days of the rush to the fediverse were chaotic, it wasn’t ready for such demand. One of the things lacking was an easy portal to help new users figure out what would work best. The .world instance for whatever reason became the more visible one as more people joined.

You’ve got a few replies to consider - don’t forget that there aren’t just Lemmy instances that see federation, there’s also Mbin (a fork of Kbin) that’s has a different feel to it and can see Mastodon blogs too.