When you enter “how to join Lemmy” in search engines one of the first results is this Reddit thread, which explicitly suggests people join Lemmyworld.

In fact, when I point people to Lemmy via Reddit, I use that post also because that suggestion actually makes it way more approachable. I think most people, myself included, are intimidated by multiple servers and feel like they’re “intruding” into private spaces. The size of Lemmyworld might help people feel like it’s more anonymous and a little easier to join as a result, especially since they are being asked to wait for “approval”, which is pretty unusual on the modern Net, let’s be honest.