We can’t rationalize, only try to understand, what we in fact do.
Although I am several yrs out now after 30+ yrs, Still, the coldness, lack of empathy and even being cold as ice of unable to see consequences (as in my case for the kids), etc. keeps me wondering me in every story I read.
I rationalized it by simply as they use randomly a switch from ‘love on’ to ‘love off’.

You are aright about loving and caring. When it was good is was good (and for many yrs. it was), when it was bad, I faced a devil
Literally almost, when seeing those eyes full of fire and her face.
It was seeing more than intense hate, more like wanting to destroy one.
I recognize that lack of empathy towards beloved one (as you told about your issue), you ‘failed’ her as her mask towards the outside world was more important.
When daughter broke up with boyfriend, guess… exw cried and cried…
mourned for not seeing him anymore
I asked her if she had the loss, or daughter… she, as he will be gone now…
I asked her how about daughters feelings and tough decision.
She replied with ‘well x (daughter) broke up didn’t she?’
IMO it is not wrong to have feelings that the ex will suffer one day too.
I don’t believe anyone who doesn’t, as it takes a very long time to reach indifference.
As they use 1 textbook only, history will repeat.
And it does in all cases on this board.
By what I am being told by exw’s intimae (another story about contact with them), already the 2nd stage is in full progress… (see, ‘how a borderline relationship evolves’).
just wait as a sitting duck... .
