Why not Jonathan?

The Philistines presented a challenge by changing the rules of fight. The representatives of each nation will have one-on-one fights. Giant Goliath was presented as the champion representative of the Philistines and demanded a representative from Israel. (I Samuel 17:1-11)
Saul excused himself: King Saul was the tallest person in Israel at that time. (I Samuel 9:2) His physical features fit him as the right choice to fight Goliath. However, Saul was looking for a man to fight. Goliath was challenging the Nation of Israel for forty days, twice in the morning and evening. (I Samuel 17:16)
Why not Jonathan? Saul could have chosen his son Jonathan to represent Israel to fight Goliath. Saul did not want to take risk, as he wanted Jonathan to succeed him as the king. Ironically, both Saul and Jonathan die on Mount Gilboa fighting Philistines later. (I Samuel 31)
Seasoned warrior: Jonathan was a seasoned warrior. He was co-commander of the first recruited army of Israel. (I Samuel 13:2) Only Saul and Jonathan had swords, while others had to fight with agricultural equipment instead of weapons of war. (I Samuel 13:22)
Experienced victory: Jonathan and his armor-bearer went daringly to the garrison of Philistine. They attacked them, God sent panic among the Philistines that they killed one another. God gave great victory over the Philistines through Jonathan. (I Samuel 14)
David anointed: David was God’s choice as the future king. Prophet Samuel anointed David to be the King of Israel, after Saul, in a secret ceremony in Bethlehem. (I Samuel 16:13)
Evil spirit torments Saul: The Spirit of God came upon David and was anointed by Samuel. At the same time, an evil spirit tormented Saul. (I Samuel 16:13-14) David was called upon to play music and calm down Saul.
David introduced to Israel: God orchestrated the war situation, to introduce David to the Nation of Israel. God gave victory through David. God groomed David in the furnace of affliction to become the greatest and most beloved King of Israel.
Do I recognize God’s purpose in each step and circumstance of my life?