Why did Jesus come at His first advent to Israel?
At His first advent, Jesus came to Israel to be the promised King according to the covenants. He appeared to the nation as the last possible son of David who could be King, fulfilling the promises and covenants that God had given to the Israelites.
Les explains that the family tree comes all the way through history until Joseph on one side and Mary on the other, and Christ is the last possible son of David that could be the King. So He makes His appearance to the nation of Israel. That is the whole idea of His first advent: He came to be that promised King according to the covenants. Paul confirms this in verse 4, writing of his kinsmen according to the flesh, who are Israelites, to whom pertain the adoption, the glory, the covenants, the giving of the law, the service of God, and the promises. God promised the nation over and over.