The scriptures indicate that Samuel was “displeased” by their request, not because monarchy is inherently oppressive. What displeased Samuel was their motivations for wanting wanted a king: “That we may also be like all the nations; and that our king may judge us, and go out before us, and fight our battles” (1 Sam. 8:20).
They had set their hearts on an earthly king to lead them in battle and give them a sense of national identity, security, and unity. Their request reflected a lack of faith and trust in their covenant relationship with the Lord. Did they think the Lord was not King enough? He had never broken His promise to be their protector, if they would but believe in Him, and had repeatedly demonstrated His power for their sakes, including their recent victory over the Philistines!
However, the power and authority of Saul's kingdom apparently started to corrupt him as his obedience fell away to pride and then to outright rebellion. In one significant incident, Saul was at a battle and Samuel was to come to offer a sacrifice, something Saul did not have the authority to do. However, Saul grew impatient and offered the sacrifice himself anyway. When Samuel arrived, Saul was rebuked sorely for his misdeed and his posterity lost the right to the kingship.
In a later incident, Saul disobeyed the commandment of God to destroy everything of the Amalekites', and instead saved the best out of the plunder. When Samuel discovered what was done, Saul made the excuse that he wanted to offer sacrifice with what he had saved. To this, Samuel said, "To obey is better than to sacrifice and hearken better than the fat of the ram."
The Lord chose David as Saul's successor, but as David's fame grew, Saul's jealousy turned murderous. Samuel mourned for Saul but no longer visited him.
After Samuel was dead for many years, Saul desired counsel for a battle he was to fight. Saul then disguised himself and consulted a witch who conjured up an apparition which prophesied of Saul's destruction in the upcoming battle.
The prophesy was fulfilled, and for a few years after Saul's death the kingdom was divided. One of his son's took over the northern tribes while David took over the Southern tribes. After much contention, David finally became king over all of Israel. Saul, like many of his successors, started out with much potential, but fell from power due to pride and jealousy.