I would purport that it was not the prodigal son’s request to obtain his inheritance early OR even that he squandered it all. Rather it was that upon receiving his inheritance, the younger son went far away from his father’s house to live for himself; and by doing so, he effectively severed all relationship with his father. Therefore we see that the true sin of the prodigal son was that he quantified his sonship in terms of the sum of money to which he was entitled by birthright and failed to recognize the true value of his sonship – the relationship with his father.
God first had to destroy the “chosenness” of the entitled Jews so that He might establish the chosenness of grace for the entire world in its place. That’s why John writes that God “came to His own, and those who were His own did not receive Him,” referring to the Jews. “BUT as many as received Him” – Jew and Gentile – “to them He gave the right to become children of God, even to those who believe in His name, who were born, not of blood, nor of the will of the flesh, nor of the will of man, but of God.” (John 1:12) This “right” is the new covenant, which is the chosenness of GRACE which is sealed by the blood of Christ and obtained through faith.