Changing His Values

I wonder why such a really nice man can be so sweet and nice to everyone,running his business on integrity and trust, and then turn around and show different values? Does this man seem to have a problem in life, or was he just putting on a show for all to see? It amazes me that he was such a person of wonderful values, yet he was such a liar and a cheat in his personal life. Did having another woman make him this way, or was he this way and I just didn't know about it? Did he compromise his values because he wanted to please someone else? What makes a man/woman all of a sudden change what they believe in?