Why did Paul need to bring a message totally different from Judaism to the Gentiles?
Paul had to bring a message totally different from Judaism to the Gentiles because the law was given only to the nation of Israel, not the non-Jewish world. Since his commission was to Gentiles, promoting Israel's law was impossible; he needed the gospel of grace, dividing law from grace.
Les explains that once law came on the scene with Israel, it was severe. Even after the cross, there was no gospel of grace in the early chapters of Acts; as an attribute grace began with the cross, but in experience it was not yet the message. After Paul was converted on the road to Damascus and appeared to Ananias, God revealed He was sending this man to the Gentiles. An apostle to the Gentiles could not promote Israel's law, because that law was only for the nation of Israel. So if Paul was going to the non-Jewish world, he had to go with something totally different than Judaism, even though he went first to the Jew and then to the Gentile. Galatians chapter two is part of that segregating or dividing law and grace.