Long story, but here are some reasons: Married more than 30 years(although I really didn't care at the time) too many family/social connections to break, the divorced OW realized he had no intentions of leaving me and turned on him by ignoring him and taking away all the attention she had been giving him(could have helped him when he was about to lose his job but didn't),he would not leave even though I told him he was free to go, and begged me not to leave him, really was through with the OW (I know when he is telling the truth now) he volunteered to go to counseling with me (knowing him, he would never have done this is the past), and he knows that despite all the posturing he has been doing before and during the affair, he really has nothing going for him;our children, grandchildren, and I are the only people who will remain constants in his pathetic life.
He really has been going above and beyond doing things to show that he realizes that his arrogance and narcissism not only cost him two jobs, but it almost cost him the loss of his family. He may hve narcissistic tendencies, but the smidgen of common sense that he had left broke through and made him realize that in time the OW who he thought was so appreciative of his talents, education,etc. was only using him to further her own agenda.
That's why I'm still with him, but you better believe me, he doesn't question me about ANYTHING I say or do now. I have learned how to be assertive, he knows I can survive financially and emotionally without him, so I now feel that I have been given a clean slate to be happy in a marriage that I WANT to be in--not one that I'm in because I'm afraid of being alone or afraid of what Mr. Almighty might do if I left.