Q&A Why Is My Ex-Husband Now Playing the Victim?

My husband was unfaithful and voluntarily disclosed his affair to me in May 2019. We tried to reconcile on and off for over a year. Each time we separated he went back to his affair partner. The last attempt to reconcile was February 2020. After several months of seeing no change, I asked him for a divorce. We have been divorced now for 6 months. He is in a relationship with his affair partner and has been since our divorce was final. The past 3 or so months when we have to interact due to our son that we share, he refuses to give me any simple pleasantries such as hi, bye, please and thank-you. When I drop our son off to him, he won't even come out of his house. Why is he now playing the victim? How or should I explain to our son who notices that his father won't even acknowledge his mother, which I think is a poor way to model respect for our son.