I haven't had much experience with lemmy at all, in order to guess, and I've seen conflicting things about them. Lemmy was already bigger and it feels like it got a lot more publicity than kbin, so they bore the brunt of the exodus. It's possible they didn't get as lucky as we did in who that constituted. The devs' weird CCP bent overshadowing some other instances' reportedly great admins just makes it even more of a confusing mess culture-wise.
I'd like to think we can abide by such stringent rules implications as "be nice." But their stated reasoning is that there's just too much content to ever hope to moderate by themselves, which.....they really should have seen coming on a platform whose intent is to federate, ngl. Doesn't matter if your homebase is young. You need underlings for this once it gets beyond a couple hundred people.
Which is why I'm leaning on the side of beehaw eventually deciding there's no choice but to defed way more than this until and unless they can afford help. With four admin-mods alone against the mercy of the entire fediverse, their hopes of upholding the mission statement will eventually be laughable any other way.
Not that I think we're nearly as bad as other places out there. I think we've got a surprisingly great atmosphere going and I hope to god it stays. But those are their two options, and kbin users seem to have an admirably civil tendency both to shitpost and to question and hear out differing viewpoints in a way I'm not sure beehaw will appreciate.