Latin was the language of the Church of Rome. Until the second century, the Liturgy was in Greek. Earlier Latin translations of the Bible were done, but the Pope knew that something better was required. So he tasked Jerome to make a new translation. As he may himself have been of Greek descent, and certainly had a first rate command of the language —as his “quarrel-mate Augustine did not, produced a first class work. But he didn’t do all the Vulgate. His work was mixed with some of the older Latin versions and then redacted over the centuries, although he did master Hebrew so to do justice to Jewish Scripture, so that by the 16th Century when the Council of Trent made the Vulgate the standard, it needed revision. The great irony is that although Erasmus had produced a new version of the Greek New Testament, and caused other scholars to look again at the Greek Bible, the Vulgate was probably a better translation of the Greek than either Luther’s or the KJV. Even now we are not sure that Jerome did not have better Greek manuscripts to work with than the ones extant, which we have to look at.
Greek was the language of the church of Jesus Christ...That is why the New Testament scriptures were written in Greek...
It would seem most Romans in that era and area would have spoken Greek...