A fantastic answer, though I'll add that OP is likely unaware that the vast majority of the "growth" on Lemmy is actually due to bot accounts. Which is somewhat irrelevant as it is still an enormous platform even after accounting for that.
Also I saw that r/ModCoord leaned more towards Lemmy, seemed somewhat biased against Kbin, and was reportedly enormously biased against Squabbles even to the point of deleting posts trying to talk about it (which not being able to check deleted posts anymore, I did not try to verify). That would make sense then that that could be why people heard about Lemmy before hearing about Kbin.
Plus the mobile app too - although I'm mostly happy with the browser view of kbin (for reading, though writing comments in it is a huge pain).