When you saw that Nahash the king of the children of Ammon came against you, you said to me, No, but a king shall reign over us; when Yahweh your God was your king.
So you do remember that he started out his career extremely early. As soon as he was weaned he was a public figure. He was there in the place of worship. The people who would gather for worship saw this little boy year by year as he grew and as he developed. They recognized that God's hand was upon this young man. He just sort of naturally grew into the position of leadership and judge over Israel.