Paul was writing to Hebrew and Aramaic speaking Northern Israelites dispersed along the northern shore of the Mediterranean.
That is who Yeshua sent his disciples to, by his own words.
Paul had limited Greek fluency, as shown by the Centurian asking him (in Acts) “can you speak Greek?”
The NT was in Hebrew primarily and soon later in Aramaic, but probably a century before any sizable part was available in Greek. The Greeks were really not that interested.
Have you actually read Paul?
Through him we have received the grace of apostleship, to bring about the obedience of faith, for the sake of his name, among all the Gentiles, among whom are you also, who are called to belong to Jesus Christ. (Romans 1:5-6)Now I am speaking to you Gentiles. Inasmuch then as I am the apostle to the Gentiles, I glory in my ministry in order to make my race jealous and thus save some of them. (Romans 11:13-14)
Because of this, I, Paul, a prisoner of Christ [Jesus] for you Gentiles—if, as I suppose, you have heard of the stewardship of God’s grace that was given to me for your benefit, [namely, that] the mystery was made known to me by revelation, as I have written briefly earlier. When you read this you can understand my insight into the mystery of Christ, which was not made known to human beings in other generations as it has now been revealed to his holy apostles and prophets by the Spirit, that the Gentiles are coheirs, members of the same body, and copartners in the promise in Christ Jesus through the gospel. Of this I became a minister by the gift of God’s grace that was granted me in accord with the exercise of his power. To me, the very least of all the holy ones, this grace was given, to preach to the Gentiles the inscrutable riches of Christ, and to bring to light [for all] what is the plan of the mystery hidden from ages past in God who created all things, so that the manifold wisdom of God might now be made known through the church to the principalities and authorities in the heavens. (Ephesians 3:1-10)