I genuinely don't know the answer to that question. We are all just left bewildered and sad, and suffering. And they become indifferent (at best) or hostile (mostly).
However, what I did learn along the way, that when he decided to fuck off, he fucked off. That left me in charge of the sinking ship. I'm doing the best I can, and sometimes I'm amazing, other times not quite. Sometimes I'm dire.
I realise, and you will too at some point, that trying to explain their behaviour is the route to madness.
Looking long and hard at yourself, and appreciating yourself and patting yourself on the back for dealing with things as and when you can, is the route to sanity.
In the interim we are both firmly in the 'mad ex-wives' category. Is that because we are genuinely insane or angry? I'd rather think it's a combination of both. But like all stereotypes, they are just other's perceptions.
And not necessarily the full story.
You can blame me for putting on a couple of stone. For getting wrinkles. For having independent thoughts. For aging. Whatever you can blame me for anything you like for me being in the position I'm in. I can, of course, do the same to you.
I choose not to. I can't see how it would help you. Normal people don't go out of their way to hurt others. They don't need to.
I write that hoping you understand fully that I'm not castigating you for doing what you're doing - after all, I'm not going to make you feel worse, I don't think anyone can, to be fair. And also because I did exactly the same thing, and some days still do. It's part of the process.
My best friend wrote me the most amazing email when I told her the bad news about why I was the woman she most admired in the world: listing all my better qualities, and noted a few of my not so good ones. At the time, all I could think was 'yes, but my husband hates me'.
It is absolutely the worst thing in the world to make your husband central to your beliefs about you.
Because it also confirms the most basic thing: there's nothing wrong with you. If there was, you wouldn't feel this way. You know you didn't deserve this. You know he chose it for you.
And you know he has chosen to do this to make himself feel better.
But really, would you hurt someone to this extreme to make yourself feel better? Really? I know my answer to that.
And that's why I know I didn't and don't deserve this no matter what.
The key to STBXH success over my mind was that he isolated me and made himself the centre of my life. I also let him.
Then he fucked off. He is no longer allowed an opinion round these parts. Despite that, he still imposes one. The he gets told to 'do one'.
I'm doing okay all things considered. So are you.
Take care.