As someone who did not handle a particular break-up very well, I can look back with hindsight and realize that no explanation for why it happened would have helped.
I didn't know it at the time, but I recognize now that I wasn't accepting the only answer that mattered--that this person simply no longer wanted to continue to be in a relationship with me. In search of a mysterious "why", I was merely preventing myself from accepting the reality of the situation. My repeated demands for a "why"--any answer given to me would be an excuse for me to argue the point...or give me a false basis for thinking that things could be fixed... What didn't occur to me, even though it was the most obvious thing in the world, was that this person didn't WANT things to be fixed.
It has been said before, but you can't explain to someone why they should love you when they don't. You can't prove your point and win a debate and someone else admits "You're right, I was wrong for not continuing to love you."
The fact that when I think about that break-up and certain things about it still baffle me, after fourteen years now, is a healthy reminder to me to that not everyone, not even the people you feel closest to, share your exact reality. Other people, even those you feel closest to, might think or feel things that you're not aware of--either because you're not noticing or because they're not sharing them with you....or, more likely, you're choosing not to know.
For someone who doesn't want to be broken up with, no answer in the world is going to help. That person, in the thick of it, will never say "Oh, I get it now. OK."
It takes time.
Even with time, there might be not BE an answer...and you'll have to be ok with that.
And even if there was an answer, there's really no answer that you'd be ok with, because, again, the end result is that someone you cared about came to a point where they didn't care about you in the same way.
I wish I'd dealt with things better then...but that's on me.
It was the reality of the break-up I was struggling with, not the lack of a detailed enough explanation...
"Don't fight the drowning, the struggle only makes it worse."
Drowning by Dear John Letters