Papias wrote around 125 AD and said Matthew wrote his gospel when Peter and Paul were setting up churches. Peter and Paul were executed about 65 AD about 30 years after Jesus died. Papias would have written also about 30 years after when the gospels were written. The church fathers are quoting the gospels early in the 2nd century then the gospels must have existed before then. Most scholars, thus, place the gospels within the first century.

Caesar Agustus was the most famous of all the Emperors and reigned at the time of Jesus' birth. "The best days of Rome were under Augustus."

We have 8 sources for Augustus. Two of them were written about his youth, cut off around 19 years of age. That leaves us with 6 primary sources for Augustus in his adulthood. There was a short funerary inscription of 4000 words. This could have been written soon after his death contemporaneously. Other than that the earliest source we have for Augustus was 90 years after his death. The earliest of these 5 sources was written by Plutarch about 90 years after Augustus died. The other 4 are written 100 and 200 years after his death. This is what we have to work with on record for the greatest Roman Emperor. Compare that with Jesus. If we take the late dating the gospels were written 30 years after Jesus that is much closer to the life of Jesus than the writings for Augustus.



https://www.namb.net/apologetics/

If we use late dates of 30 years after Jesus' death for the gospels written and recorded, we shouldn't think that was when pen to paper was first initiated. The many notes a writer puts together when doing a biography are first collected and compiled over years. We shouldn't think the writers of the NT are like mechanical ghost writers jotting down whatever pops into their head. Also, we can easily fill in the gaps by the other books of the New Testament from Paul, James, Peter and again John from the years following Jesus' death.