Why did Paul go to the synagogue first before preaching to Gentiles?
Paul went to the synagogue first because in his early ministry he always went to the Jew first, where he would at least have a halfway civil hearing. When the Jews rejected the message, he then went out into the Gentile area, the marketplace, and other places.
The transcript explains that Paul’s early ministry pattern was to go first to the Jew. He chose the synagogue because there he could expect at least a halfway civil hearing; only after the Jews rejected the message did he move into the Gentile area, the marketplace, and whatever places he could reach. This pattern fits the wider context of Paul repeatedly defending his apostleship, since he faced the slur that he was an imposter, not a true representative of Judaism, but a renegade Jew. He had to defend that he was God’s man for the hour.