Politically speaking: Why can't most men stay faithful in a relationship?

What is wrong with these people! So the reason former California governor Arnold Schwarzenegger and Shriver split is because he had a child with another woman over a decade ago that just came to light. Of course, he isn't the only politician (or person in general) to admit to such a thing. There must be a chemical imbalance in mens brains that propels them to cheat. What do you think?