Now I am speaking to you Gentiles. Inasmuch then as I am an apostle to the Gentiles, I magnify my ministry in order somehow to make my fellow Jews jealous, and thus save some of them.
Romans 11:13-14 ESV

I’m sure Paul would rather have gone directly to the Jews as he did early in his ministry. However, since they rejected him in his direct approach, he was determined to follow the calling that God gave to him in the hopes that the grafting in of a mixed multitude of Gentiles would provoke more Jews to put their trust in Yeshua.