I suspect most people who joined Lemmy ended up on .world because they would have gone here first:
For a while Lemmy.World was one of the first ones you came across; between that, the open signups and the “general purpose” moniker, rapid growth was probably inevitable.
Add the fact that lemmy.ml and others were/still are doing applications for sign up instead of an automated system. I applied twice for a .ml account and never got a single response, not even a denial or “your application is being processed”. I have no idea if my application was ever even seen.
On the other hand, I signed up to lemmy.world and kbin.social in minutes and have been using them ever since.
I was tempted to join .ml but the banner at the top of the application form was discouraging. Went to .world and here we are.
