I think most people would agree that in many many cases there are red flags that are missed. But blaming women for this "oh, why didnt she leave before she had children?" "why did she let it get that far" is the bit of victim blaming that gets people's backs up.
Because the reason she didn't spot it or didn't leave is complex, with many layers. In SIL's case she'd been told by her parents for years that she was too fussy, that she kept letting "good men" go because she had ridiculous expectations. They told her over and over again that she was getting old and if she wanted children she needed to get on with it and stop ending perfectly good relationships. This is further complicated by the fact that she has always been seen as the irresponsible, silly, unreliable one - even though she's the one who bends over backwards for her family. On top of that, she's a kind person and exBIL presented as someone who had experienced a lot of trauma and just needed some love and understanding to build his confidence. So between that and her family, she felt she deserved his behaviours. And I don't thik it's a coincidence that she only FINALLY started making moves to end it after PIL finally started to see what he was really like and supported her (and quite honestly, that only happened because I lost my temper and pointed out some home truths to them a few times).
So yes, we need better education. we need men to step up more. we need to all stop accepting shitty behaviour or saying things like, "oh, what are men like? haha". We need men in the workplace to stop getting away with both the obvious and not so obvious sexist, misogynist statements and activities (and lots of abuse is based in sexism and misogyny - which is why I think we see it more from men to women or women to children: it feeds into society's existing expectations of power and what's okay etc). We need popular culture to make it clear to teenagers and others that the drama and controlling behaviours are NOT a sign of real love.
And it's not always easy. I'm that woman who calls out things and can SEE people rolling their eyes at my "rampant feminism" or whatever or I get told that I'm too sensitive or I'm seeing sexism where it doesn't exist. And yet, on our school run there are plenty of men doing the school run - brilliant you think? Except I've spoken to many of these men and many of the women and you know what I've noticed - the men only do school run if i's convenient. I've never ONCE heard one of these men say, "yeah, it's a bit tricky because I have to be a bit late on wednesdays as I'm doing school run, but Mary absolutely can't be late on Wednesdays so I have to suck it up" and yet it's something I hear from women over and over and over again. It's such a small thing but it' s asign of the imbalance and different expectations for men and women.