In biblical theory, the reason for writing the New Testament

In biblical theory, the reason why the New Testament was written was because the illiteracy rate in the Roman Empire was very high at this time, and Christianity in this period was not peaceful.

For a new religion that just broke away from Judaism, it is normal to have different views on the doctrine and the future development direction of religion. Even if a famous theologian wrote a book with far-reaching influence on later generations, how to make it accepted by believers and priests at that time is still a long process, which has to mention another question.