Kbin is doing pretty well, they are still holding on to about 6,000 MAUs. Lemmy still has around 32,000, for comparison. Lemmy peaked around 66,000 MAUs at the end of July, but a big chunk of that was probably alt accounts that have since gone dormant.

Kbin's main developer had some major IRL events that coincided with the reddit exodus so he wasn't really able to do much work on the code for a while. But now he is back, and another team has also made a fork of kbin called mbin.

https://kbin.social/u/ernest

Federation is still pretty janky with kbin, so I think that activity should pick up on both sides once we get some software updates and more intermingling of the kbin and Lemmy userbases.

OP is also spot on about this being the largest that a reddit alternative has ever gotten. I'm pretty sure alternatives such as discuit, squabble, tildes, etc have never even approached 10k MAUs, so we are already well past that. If not for the fact that this platform is federated, there would probably already be much more activity. However, the federated structure should become more and more useful as we grow larger, so it's a worthy sacrifice even if it's stunting activity for the time being.