Why?
Because the process of self-delusion occurs. He must delude himself into believing the behavior either isn’t wrong or is a much less serious than it actually is.
Intervention is making the person face the truth about his or her behavior.
At the very moment a person accepts that truth about himself, he usually accepts the path of healing offered by those who brought about the realization.
Break through the self-delusions and you have the opportunity to put the person on the path to recovery.
I thought the same thing over and over. What did you think about me and the kids while you were with her?
My husband's answer is I didn't. They compartmentalize so they can keep their worlds separate and it fits their "needs" 
It will bother you for a long time because women and men's thought process is different. You are wanting logical understanding to an illogical situation.
I got the "I don't know answers" as well and told him that is not an answer, that is a child's response but even in his IC and our MC, he could never convey the WHY.
The MC finally said, he probably doesn't really know why.
Very frustrating I know.
Keep probing but know you will most likely never understand the WHY to satisfy you head or your heart.
Good luck.
