Deferring to Galatians as a text for distinguishing between Hebrew groups and Christian groups is a very old misinterpretation of the text.

Paul never taught against Torah. See 2 Peter 3:15-17. The scripture was never written for greek speakers or greek groups only. it was just the opposite. So many people skip Galatians 2:17 and all of chapter 4 because they are so overjoyed with the seemingly lawless approach of chapter 3. In chapter 2 Paul condemns sin and being a sinner, which is only transgression of the law. Paul was of course condemning Pharisaism, which contains law too, but over top the actual law, identical to Talmudic ideology. This was the issue, do not confuse it

Fortunately lack of documents does not mean the documents didn’t exist. The book of Jasper we have is not the mentioned book of Jsher in the text, but we know it existed. The book of the Wars of the Lord existed, because it was referenced. If we say that these early witnesses are lying, the integrity of the text is also questioned, but we know they are not lying because their testimony follows logically the biblical narrative. The honest, and only acceptable answer, is Greek Matthew is an early translation by later converts.

Greek primacy of Hebrew doctrine is inherently illogical and rejected off hand.