Cheaters

What makes men cheat? Do you think they do it out of pure evil or do you think there’s a motive behind it. My best friend cheated on his soon to be wife with another women 5 or 6 times. She was saving herself for marriage. He confided to me that he was madly in love with his fiancé but he “needed” sex and physical contact which he wasn’t getting at home. Do you think this is true he’ still “Madly” in love with her? And he cheated just for contact