I think physical abuse is often a learned behavior on an acceptable way to handle emotions. As well as a learned way to control someone. Maybe this is how he witnessed men treating woman while growing up. When something like this is ingrained, it is extremely hard to UN-learn and replace with acceptable means of handling emotions.
He is probably not capable of real remorse or sorrow, only the kind of remorse that will get you back so he can continue to have control.
In addition, woman who stay or go back is often a learned behavior of being treated unacceptably and having low self-esteem. Often when the carrot is dangled in front of them (flowers, gifts, “words” of sorrow, empty promises, etc.) they go running back only to repeat the cycle all over again.