Why was Saul tormented? Because he had thrown away the future leadership of Israel for his posterity.
How had he done this? Because of political expediency.
He had used his own judgement instead of relying on the prophet Samuel. Saul felt he could not wait anymore because his soldiers were deserting before the battle with the Philistines, so he offered animal sacrifices when he did not have the religious authority to do so.
His growing reliance upon his own judgement was further evidenced when he, King Saul, was instructed by God to destroy the Amalekites completely, every man, woman, child and even beast. Saul adjusted the commandment of God but spared the king Agag and some of the best looking animals (see I Samuel chapter 15, verse 9). Again Saul had disobeyed a direct instruction of God, using his own judgement. Obviously the prophet Samuel was displeased and pronounced the distressing news (see verse 23). As Saul had rejected God by preferring his own judgement, so too God rejected Saul.
Even though Saul appeared to repent, it was probably not sincere, when he pleaded with Samuel to forgive him, it seemed to be for honouring Saul before the elders of Israel (verses 24 - 31)
Even though Samuel acted sternly with Saul, in private he wept all through the night (see verse 11)
When one looks carefully at the conduct of Saul, it is clear that he sought to twist God’s will to support his own ideas and judgement. Saul acted, then he tried to get God to ratify his own decisions. Clearly this once humble man had become arrogant with his power as the King of Israel. Saul, it can be shown, seemed to make himself the “God” of Israel. This was classified as rebellion by God, even as witchcraft!
In one battle the foolish king commanded his men to fast before they went into battle. To force God to give the Israelites victory. His son, Jonathan, was unaware of this royal edict and in battle with the philistines, he ate honey. When Saul found out, he commanded that Jonathan, his own son, be put to death. The armies of Israel refused as Jonathan was the hero who had turned the tide of battle in favour of the Israelites. King Saul was forced to rescind his own order, I don’t know if he was relieved or vexed.
Saul after the various wars, wanted David in his own court. David was a very talented fellow, much loved by Israel. The jealousy of King Saul knew no bounds as he repeatedly tried to kill David. Yet when Saul came to his senses, he begged for forgiveness, but his repentance was in vain. The evil spirit came upon him again and again, then he would try to kill David.
He had no way out of the terrible course he had chosen, he was under the power of the Devil.
I feel sorrow when I read of the terrible internal struggles that King Saul lost. What a glorious future he could have had.