My best friend sabotaged each of his three long-term relationships because he kept getting cold feet when he got to the engagement stage. All three of those women ended up marrying other guys, but two of them are still fond of him, judging by their behavior at the class reunions. And to this day, he still has strong feelings for both of those women.
So your ex might really miss you and want to get back together. And he still might have a fear of commitment that he can't overcome. I don't really understand the thought process and I have pushed my friend to get therapy, but he bailed on that after one session.
Good decisions come from experience. Experience comes from bad decisions.