“I am in great distress,” Saul said. “The Philistines are fighting against me, and God has departed from me. He no longer answers me, either by prophets or by dreams. So I have called on you to tell me what to do.” (1 Samuel 28:15b NIV)
Saul was chosen by God to lead Israel. He was gifted, strong, and charismatic. But he had a pattern of behavior in his life that revealed he would not trust God enough to obey Him. This went on for such a long time that, finally, God could not use him anymore and chose David to be the new king.
Initially Saul had liked David, but when he discovered that David was to replace him on Israel's throne, he would not surrender to God, would not surrender his crown, would not obey God. Finally, he ended up turning to the occult. He went to visit a woman known as the witch of Endor to ask her to conjure up the spirit of Samuel the prophet, an occult practice that would have been an abomination to him when he was a young man. As G. K. Chesterton wrote, if people cease to believe in God they do not believe in nothing but in anything. In the end, Saul took his own life in despair rather than bend his knee before God.
-- John Ortberg in Faith & Doubt