Kbin was just a year old when everyone went there. It went from a few hundred to a couple thousand and then to 50k users in a couple weeks. It was literally one person, @ernest, until a few weeks ago. Lemmy has had a few years of people working on it, an active subreddit for a few years. The Lemmy creators were active on several subs for years. It’s not a surprise that kbin just now has more than one person working on developing.