Paul is from the city of Tarsus, which was multi-cultural, multi-ethic and there was likely very little separation between Jews and Gentiles which is an important detail because Jews, particularly Pharisees, were zealous about remaining distinct and a part from the rest of the world, just as God called Israel to be a model and example to the rest of the world and also a nation set apart.

"Wright: There are two things which are in hindsight, apparently intention. And when I've talked to Jewish friends about these, I think they are both still in a kind of tension in the modern world as well. One is the sense of the people of Israel, the Jewish people, being designed by God to be distinct from the rest of the world, and to be God's special people, the ones who have a special closeness to God have to maintain that.
Then, in the Second Temple period after Ezra and Nehemiah, on through to the time of Jesus, the zealous Jews like Saul of Tarsus - that's the word he uses of himself. He says, "I was exceedingly zealous for the traditions of our fathers" - they are looking back to the great traditions of zeal to people like Elijah and Phineas and Elijah in 1 Kings, and Phineas in the book of Numbers, and saying, "That's what it means to be a zealous Jew."
When Israel is going to the bad, worshiping the Baal or whatever it is, then somebody has to step in and do what's necessary to purge the evil from Israel. So you have that great biblical tradition which is what inspired the Maccabees. If you read 1 Maccabees 2, great speech in there about what you now have to do granted the wicked Syrians who are coming to take over and they want to stop us all being loyal Jews. So that's clearly where Saul of Tarsus came from. That's historically a puzzle." NT Wright, Bible Project Podcast

https://bibleproject.com/podcast/series-gospel-p9-acts-e5-nt-wright-interview-getting-know-apostle-paul/