Why did Satan oppose the gospel going to the Gentiles more than to Israel?
Satan opposed the gospel going to the Gentiles because he especially hated it reaching the masses of Gentiles, not merely Israel as throughout the Old Testament. He stirred opposition through believing Jews, those still steeped in Judaism, and satanic power, causing Paul to suffer for preaching to Gentiles.
Les explains that Paul was appointed a preacher, an apostle, and a teacher of the Gentiles, and that his chief opposition came first from the Jew—believing Jews as well as those still steeped in Judaism—but it was not the Jew alone. A satanic power opposed him from every direction because Satan did not want the gospel going to the Gentile world. Les says Satan hated that the gospel had gone to Israel throughout the Old Testament, but the gospel going to the masses of Gentiles was the last thing he wanted. Paul therefore suffered these things, yet he was not ashamed, for he knew whom he had believed, never doubting God despite difficulties, sickness, sorrow, and suffering.
For the which cause I also suffer these things: nevertheless I am not ashamed: for I know whom I have believed, and am persuaded that he is able to keep that which I have committed unto him against that day.