I heard a very illuminating sermon on the Septuagint this past December.
Greek was the international language at that time, and the apostles most likely had scribes and followers who composed their teachings into writing and transmission to the various churches.
But in regards to the Septuagint, the priest said that 200 years before Christ, Emperor Ptolemy of Egypt wanted to build the biggest library in the world and he wanted an authentic copy of the books of Sacred Scripture. He selected 70 rabbis who came to Egypt and were separated from each other and asked to compose the books. It is assumed they had their own scribes. When they were completed, all books were compared to each other, and what was miraculous is that of all the 70 rabbis, every book was identical to each other, word for word! We cannot but say this is a miracle of the Holy Spirit.
This interpretation of Scripture anticipated the Messiah as we know Him. The apostles and St. Paul also followed the Septuagint.
Two hundred years after Christ, Jewish rabbis came together to have their Hebrew version, the Mazoretic, that had some parts that did not anticipate the Messiah as Christians. When they were forming their books likewise, there was alot of disunity and disagreement among them. One could say, well when you have 2 Jews arguing, it is like there are 3. Anyway, their books were completed.
And this interpretation had parts those could be accepted by those of the Septuagint, and as people lived among one another, it is natural there is like an osmosis of ideas back and forth.
Martin Luther wanted to go back to a ‘pure’ understanding of Scripture and lost faith in the Church’s stand of apostolic succession. He wanted to remove some books that supported his particular theology. Of course, he followed that which prophesized the coming of the Messiah.
Our Lord drew from OT prophetic statements to reveal He was that Israel had anticipated.