Interestingly, it's not important to "understand" someone else, because as hard as we might try, we can't understand another person.
If you want to know my opinion? He wasn't feeling it anymore in the relationship and he was too big of a coward to tell you up front. that's what i think.
I'ts NOT your fault if this is the case. Sometimes feelings fade and we want to move on. In my world, i'd be up front. But he had to make up some lie. In this case, it would be that he said he's moving, but you don't think he is (intuition tells us a lot too).
Wouldn't it be nice if people could just set us free with the truth? the truth is too difficult for some people.
And again, honestly i don't think we need closure. I truly don't.
You deserved better, but you didn't get it. I'd let it go and move on the best i could. Perhaps in a matter of weeks or a few months? You'll make some of your own discoveries why you two weren't compatible anyway.
He wasn't "heartless".... he's just a coward. Be thankful you're no longer with one of those