What are your dates and evidence? Is there anything beyond, “because I say so?”
And that leaves the question of what is authoritative in the absence of Holy Scripture? You will agree that there was a time that the Church had no New Testament?
How reasonable is it to think that a largely illiterate culture would be expected to rely solely on writing; whenever that writing got written.
The culture was not as illiterate as Roman Catholics claim. Granted there was no universal literacy, but the were not barbarians.
Jesus was literate, was He not? He was the poor son of a carpenter. The NT writers were literate. A big jump to say largely illiterate.