He fucked her left and right. She enjoyed being with him. He was big, strong and knew how to blow her whistle. He knew how to reach her body and soul. She was there because he had all the skills that woman needs from a man.
He was perhaps a smart guy. He convinced a married woman to occasionally sleep with him which she did when he had an urge for her. In order to befriend a random married woman for romantic affaires requires superb skills and manipulation. He had those skills.