That does seem to have changed since I last cared to look. As dannoffs pointed out - it seems lemmy.ml was unlisted from the join-lemmy.org instances page where previously it was listed as #1 for the Popular section. They also removed the ## users / month metric so the list is no longer guaranteed to be sorted by popularity.

Just last week - lemmy.world was reporting as 87 users/month and lemmy.ml as 1.6k users/month:

https://web.archive.org/web/20230608170721/https://join-lemmy.org/instances

This has of course changed - and unlisting the instance so that it isn’t the most popular instance likely has a lot to do with that. That seemed to happen sometime in the last week - I cbf checking every wayback timestamp to see exactly when.

I’ve been using Kbin myself so haven’t been following Lemmy very closely. Only whatever happens to reach my page over on kbin.