Kiyoko, and all of Tobs' characters have always been really popular.
I've never done her content, but every time any poll has been done Kiyoko and Brienne have come out on top (and usually Cait too). She's really popular.
The opinions around here are a vocal minority. Azzy is my favorite companion by far, and she barely placed in this poll.
No offence and nothing against you, but i hate so bad the vocal minority spew, and in this case it makes less sense than usual too.
Cait got 3rd place because she may just be the companion with the most content, and surely the one with the most presence/interactions in the main story and otherwise. And even then she got placed 6th place and lower more times than she did 5th and higher, as opposed to Brienne and Kiyoko who
mostly got placed 1st and 2nd. That's not really a good thing, and if anything speaks of her relative unpopularity.
Plus, concerning Kiyoko and Azzy, i'm pretty positive most around here like the former just fine and dislike or don't care for the latter, so there's also that. Don't lurk a whole lot on 4chan, but i'd say the only character that's more disliked here than over there is maybe Agni, really. Even Keros got more or less the same reaction.
But anyway, kind of a sadsack poll. After ranking Brienne, Arona, Etheryn and Kiyoko, it was honestly just easier going straight to the 11th place and work my way up