In Romans chapter 9, we saw that all who were elect within Israel would be saved. God previously revealed that all Israel would not be saved; but some Jews were saved – a remnant. Also God had spoken long ago of His plan to use Gentile salvation to provoke the Jews to jealosy … so we cannot at all say that God has failed. Romans chapter 10 reveals that the failure of Israel to believe is their own fault – not the fault of the Gentiles, and not the fault of God.
Israel heard the message; they understood the message; so they were without excuse. However, what made the Gospel so offensive to them was that Paul was preaching a Gospel of salvation by grace alone (apart from works of the law). Paul preached that the Law was set aside, but the Jews sought to be justified by their works. If only God would even credit them for trying, they would welcome the gospel, but grace insists that you bring NOTHING to the table.