No one knows who wrote the Gospels, although we can be certain that the Matthew Gospel was written by people with a Jewish background.
Likewise, the authors of several letters attributed to Paul were written by unknown authors. Paul, of course was of the diaspora and he had no affiliation with the community at Jerusalem. He shows this at Galatians, despite the religious fiction written by "Luke".
No one knows who wrote 1 Peter and 2 Peter, the latter most likely written about 100 years after Peter's death. The latter is an exposition of Jude, which in turn is based on 1 Enoch (a book commonly used throughout the NT). The author of Revelation is not known but he was definitely had a strong Jewish background.
The people who decided which writings would be accepted as Christian Scriptures and hence form the NT were not Jewish.
Each writing had to reflect the culture of the community that produced it. None of these original texts exists, and those texts we are left with have been modified to include the views and opinions of successive copiers and their communities. Thus we need to identify the idioms, understandings, religious and secular politics, geography, interplay with neighbouring communities at each time, and so on.
Further, when we come to the NT writings, the feature known as Pesher comes into play. This term, which finds its genesis in the Dead Sea community, says "this is that", applying Scripture to their own times while totally disregarding the original context of the text. We see this practice in Jesus' "explanations", as well as in Paul's and Luke's. Today, we see the WTS employ this method, when they say that the Scriptures which were written thousands of years ago, are speaking of them. This, I believe, is the reason they reject Higher Criticism while at the same time as accepting Lower Criticism.
Doug