Because the visual of the bigger, aggressive one having darker skin than the smaller, feminine one is part of what makes it “sexy.” It’s rooted in how white America sexually objectifies and dehumanizes Black men.
If you care so much about these characters and their story, why is the majority of the fan art just the “tan” dude being practically naked and in chains while being owned by a (full dressed) white blonde dude?
I’m all for queer stories toying with gender roles and adore enemies to lovers.
But this visual has racist subtext that I don’t think many white women in particular understand, much less have considered that it is part of why it appeals to them.