Why did Israel reject God as their one and only King?
God intended, from the time his people entered the land of milk and honey, that he would be the sole King over his people. He used individuals called Judges to uphold his laws, save Israel from its enemies, etc. but always retained to himself the right of sole Ruler. The office of Judge, unlike that of a king, could not be passed down to a person's descendants.
Gideon, who was a Judge over Israel from 1145 to 1105 B.C., was used by God to free the people from a hated enemy. He was so successful in battle that the people wanted to make him king! Gideon, in an act of humility, reminded the people that he could never rule over them as they already had the Lord governing them! He told all Israel, "I will not rule over you, neither shall my son rule over you. The Lord shall rule over you" (Judges 8:23, HBFV).
What caused the people, years later, to demand that a human, and not God, be their ruler? The answer lies in human nature and its desire to live its life apart from the Eternal.
In brief, the story concerning how Israel came to have humans kings begins with the prophet Samuel. He began his service as Judge in 1085 B.C. Thirty-two years later, in his old age, he decided to give his sons Joel and Abiah the same responsibilities he possessed (1Samuel 8). Unfortunately, the sons soon began to take bribes and pervert justice. Their corruption became so well-known that it motivated the elders of Israel to make a special request of the prophet, ". . . appoint a king to rule over us, so that we will have a king, as other countries have" (1Samuel 8:5).
Samuel initially believed that the Israelites disapproved of his personal leadership and guidance of them. God, however, soon revealed to him what was really happening. The Eternal stated, "'You (Samuel) are not the one they have rejected; I am the one they have rejected as their king'" (1Samuel 8:7).
Samuel is then inspired to anoint Saul as the first human monarch over a united Israel (1Samuel 9:15 - 17). Saul's reign lasts for forty years (1050 - 1010 B.C.). Because, however, he refused to obey God's commandments (1Samuel 15:10 - 11), his descendants were not allowed to assume the throne. Samuel is then sent to anoint a young man of the tribe of Judah, named David, as the new king (1Samuel 16:11, 13).
David is first made king of Judah before becoming ruler of all Israel. He and his son Solomon each reign for forty years. Solomon's sins, however, causes God to reject his people again by causing the nation to split in two during the reign of his son Rehoboam. The total length of time a united Kingdom is ruled by a human king is only 120 years (1050 - 930 B.C.).