Kylo Ren has wanted Hux almost from the moment they met, despite neither of them actually liking each other that much. Snoke was well aware of this and uses it to his advantage.

He promises Kylo, that once he deems him ready, he will give his prized General to him as a gift, allowing him to do whatever he wants with him.

That time has come, whether Hux wants it or not.

(Anon can have it end up being consensual, dub-con or just straight out non-con, I don't mind either. )