Paul recognizes that, for the most part, the Jews have rejected Jesus as the way to salvation. Given their history of having a relationship with God, they should have been the ones to accept Jesus. Ironically, the ones who should naturally have been part of God鈥檚 people are broken off and the ones who should not have been, the Gentiles, are grafted in. Paul warns the Gentiles that they need to recognize they are not the natural branches. In other words, there should be no room for anti-Semitism among Christians. He then says that in the future, things will turn around. There is a day coming when Israel will be spiritually revived. Paul closes this section of Romans in praise to God because he has demonstrated the righteousness of God in his dealings with humanity.
Who has accepted Jesus and who has rejected him is a mystery. Paul and his fellow Jews had the most reasons to trust Jesus, but it took a miracle for Paul to believe, and most others never did. Gentiles had almost no exposure to God and lived lives that completely ignored God鈥檚 standards. It seemed obvious they would never come to Christ, but somehow they did. It is never our job to determine who will believe and who will not. We tell people about Jesus and leave the rest to God.