I suspect it's also affected by people not having Sheen in anything before, Googling his other roles and/or seeing interviews, and going WHOA FUCK (for a variety of reasons).

As has been commented, he has strong Chaotic Weird energy.

https://upstartgeek.tumblr.com/post/185632910393/michael-sheens-a-great-fav-to-get-into-because-on

And also fandom's eternal and glorious polymorphous perversity, of course.