Saying everyone who's into Kylux has a Nazi kink is... pretty gross of you, anon.

Pretty sure the reason so many people like the pairing is because of some combination of:
a) hatesex
b) they obviously drive each other nuts, but are also stuck relying on each other - so, fun dynamics
c) it's refreshing to have a pairing where you can write those stories just totally fucking one or both of them over, and you don't feel the slightest bit bad about it, because they're both horrible people
d) a lot of anons here also seem to have a particular interest in daddy-issue tropes, and this pairing has that in spades