big wow. much member. so large.

The lemmy.world statistics are visible from the home page. There are currently 130,000 registered accounts on lemmy.world which is far larger than any other lemmy instance. Primarily because most other instances had restricted registrations of some sort for awhile.

I can’t think of any other website of a similar style that is larger than the entirety of lemmy. The next biggest might be kbin.

Remember, lemmy et al., is not a commercial/corpo run forum. It has no monetary incentive to grow exponentially every quarter. There’s no shareholders or BOD to bootlick. Let dot world grow organically. Sometimes it will even shrink but one day it may spurt.

https://fedidb.org/current-events/threadiverse might answer at least your first question, tho I have no idea how accurate those numbers really are so take all that information with a grain of salt.