Honestly, as long as they are compelling, people will like them. There's a reason why Rey and Kylo Ren are shipped together in the movie. Regardless of where it ended up, that type of story is interesting.

Also? The whole aspect of "good verses evil" morality can be timeless to some people. But there's a long-standing trend to see more morals with nuance.

Lastly, their motivations can be compelling enough.

Also? Look at how Loki is treated in Marvel.