Why did arnold schwarzenegger get divorced?

Many people were surprised to hear of the break up of Arnold Schwarzenegger and Maria Shriver, until Arnold revealed his infidelity. In mid May 2011 Arnold admitted that he had fathered a child outside of his marriage. The woman with whom Arnold had the affair, and who later bore his child, worked in the Schwarzenegger home for 20 years. Maria and Arnold are currently separated, but all indications point to a divorce in the near future.