The Quillette article (subscription only) What Explains Women's Fascination With BDSM Fiction? - "Every generation or so (i.e., roughly every 25 years) a woman (it’s always a woman) writes a book about kinky sex—and a very specific type of kinky sex..." is on my sidebar.
I don't think I have ever commented on this, but I thought about this years ago, and the simplest answer is that it is not about a desire to be controlled, or quasi-raped, no matter how handsome and dashing the Duke is. Quite the opposite. When one is reading a book, even more than when going to a movie, one can put it down at any time. Unlike a husband, boyfriend, or even a date. One can choose an author whose works are similar but safer if it's too hot. The woman is in complete control of the experience. I mean, if you get to choose your rapist and pretty much write his dialogue and direct his actions, relying only on the descriptive talents of a sister who you have already vetted for being in your range of artistic enjoyment, it's not really rape, is it?
Too steamy, too rough? There are things available one level gentler or ten levels gentler. Or you can take the spice in small doses. Everything is a la carte. Like women misunderstanding what men's pornography means, men misunderstand what this women's pornography means. Or feminists misunderstanding what girls' fantasies about princesses (or Barbie) means. Princesses do whatever they want and order everyone around. If they have a prince, he is decorative and mostly silent and obedient. He is the proper reward for being a princess. Write his dialogue, script his actions. Barbie buys whatever she wants, wears whatever she wants. That's what they like.
I'm not saying any of it is especially healthy, I'm just saying it's different from what is popularly supposed.