Considering 'why women have these fantasies', I partially disagree. Women are vulnerable to this kind of 'propaganda'. Women write a lot of this stuff, and I'm not convinced it's just regurgitation. I don't know if women would fantasise about this kind of thing if they weren't exposed to explicit examples of it, but just by living in a patriarchal society, it's impossible to avoid eroticised power displays. Once you've seen them, how do you process them?
When you come across something unfair, or disturbing, or traumatic, it's natural for you to psychologically prioritise processing it.
Internalising that 'it's sexy when men are dominant over women' is one way. We're encouraged to believe this. Because, in my opinion, that type of domination is inherently violent, and violence expresses domination, that becomes 'it's sexy when men hurt women'. And then women write or fantasise about this stuff. Whether or not they're authentically invested in the premise - it's a way of digesting how we culturally perceive men, women, and their relationships.
I think it's a consequence of living in the conditions women live in. Basically -
1. Gender is sexy. Gender is deeply eroticised, and involves a lot of the sexual scripts people learn and rely on. Man aggressive, woman submits is just exaggerated gender.
2. Catharsis. There doesn't need to be any personal, individual trauma for living in a patriarchal culture to affect women. The pressure to conform to gender norms and scripts, the awareness of women's vulnerability, and constantly having to navigate gendered expectations whether you want to or not can create a powerful sense of relief if you just give in.
3. A lot of women are probably very bored. Cosy romances are popular, but also not very interesting. Genuinely passionate, erotic, and interesting character dynamics are hard to write and can't just be churned out for profit.
3.a. The cultural ascendancy of the concept of male sexual abuse as the expression of women's sexuality means that this kind of thing becomes normal; the default; the easy fantasy to reach for. And hey, it makes you hot, it makes you interesting (but only in a cool, socially validated kind of way), maybe it makes you seem less bland and boring to yourself.
3.b. Violence is cool. This goes well beyond erotic fiction. Violence is gendered. Women 'like' cool men, and their 'natural' place in stories with violence is as the victim.
3.c. Erotic fantasies aren't where most people want to start tackling their preconceptions of gender and narrative gender roles.
4. If she isn't satisfied with her sex life, it's probably because she isn't satisfied with her sex life. She might just think kink is an easy fix to restore excitement, rather than trying to find her husband more sexually exciting, address anything affecting her sexual attraction or enjoyment of sex, or try new things without a power dynamic.
5. These books sound like 'romantic' whump. I feel like 'why women like whump' is a slightly different topic.
It would be interesting to read about whether there's any correlation between kink and class or occupation. Arguably, very enclosed, under-stimulated and under-active people might feel more interested in recreational violence. Conversely, violent 'sports' were much more common when most people did hard manual labour, so maybe not.