It is hard to explain for a layperson like me.Experts have explained traumabonding very well.Google it and see if you can relate.My suggestion is to stop thinking about him and try to educate yourself. Posters have already suggested some psychological phenomena. Please Google those and read up.A lot of times people like us can't imagine these maladaptive behaviours are actually abuse.Our minds just donot function like that.We try to come up with some kind of logical reasoning for illogical behaviours. That confuses the hell out of us.So it is very important to read up on this and get awareness.