Nicole & Tom Weren't Married in the Eyes of God
Nicole Kidman was able to marry Keith Urban in a Catholic Church, because her marriage to Tom Cruise wasn't recognized by the Church. Catholic rules state that you can't be married twice by the church unless your marriage is annulled. Many believe that Nicky had taken this action in order to marry Keith. But almost 10 years is a little long to plead that you didn't mean to get married.
The Catholic Church in Australia didn't see her marriage to Tom as a spiritual one and only as a legal one. Basically, it never happened in the eyes of God.
However, it was very real in the eyes of crazy.