What opened the door for Paul's ministry to the Gentiles?

Les explains that after Saul of Tarsus met the Lord on the Damascus road, the Lord said to him, “Go thy way, for he is a chosen vessel unto me, to bear my name before the Gentiles, and kings, and the children of Israel. For I will show him how great things he must suffer for my name's sake.” Les says that statement opened the door to Paul's ministry among the Gentiles. This came at a crucial transition: Judaism had clout with Rome, and Saul and Israel's religious leaders had been pursuing renegade Jews who followed Jesus, even to Damascus, imprisoning and putting them to death. But with Israel's continued rejection, the prophetic program of Jew only came to a screeching halt. God's time clock stopped, prophecy stopped, and God opened a whole new vista of Scripture—the mysteries. Paul writes in Romans 16:25 about being established according to Paul's gospel and the preaching of Jesus Christ according to the revelation of the mystery. Les notes that for almost two thousand years we have not been in the prophetic program but in the Age of Grace, the revelation of the mysteries, things kept secret in the Old Testament, with no concept of Gentiles being brought into relationship with the Almighty God.