Making fun of people is bipartisan, but over the last 10 years making fun of certain kinds of people became partisan. Since a lot of the lolcows on this site are degenerates, trannies, or fat, leftists aren't "allowed" to criticize them, because leftism became about identity ideology instead of political policy. So the audience that remains self-selects for non-leftists, and lefties that
wanted to continue on the left politically but got pushed out for some wrongthink. (There's a lot more of those here than you realize.)
There's also the right-wing refugee effect others mentioned. Also there were a series of radicalization events specific to KF: the monthly tranny DDOS, #DropKiwiFarms, Liz Fong-Jones continuing deplatforming, And of course the ongoing debanking for leftist morality reasons, which Null has spent literally a third of his life trying to fight.
A site with this focus and history is arguably incompatible with a proper, full-on leftist mindset. Take out the identity politics from the modern left, and what does it consist of? Leftist style government and economics? The government has screwed KF over and subsidizes its enemies. I guess you could be left wing economically and right wing on everything else, but I've never met such a creature. (Except maybe
Nazbols, we got a few, but they usually get classified as right-wing.)