60-70 gospels is nothing but speculation and the idea that the bible as it is today coming years after the events is also another speculation.
A casual reading of the bible reveals that it is 'time conscious' book; every event happened at the very specific minute/second that it was intended from the beginning by God.
You'll notice Jesus using phrases like "..my hour has not come or my hour has come..", even His birth was at specific intended minute that divided time/age.
Jesus would also use phrases like "..whosoever readeth.." clearly showing that there was specific intention to put it down in writing in the beginning.
There's a combination of these two things (time consciousness & intention to document) which proves that the bible was miraculously documented as intended by God from the beginning and not later but immediately as was revealed/inspired.
Rev 1:
1The revelation from Jesus Christ, which God gave him to show his servants what must soon take place. He made it known by sending his angel to his servant John, 2who testifies to everything he saw—that is, the word of God and the testimony of Jesus Christ. 3Blessed is the one who reads aloud the words of this prophecy, and blessed are those who hear it and take to heart what is written in it, because the time is near.
Rev 14:13Then I heard a voice from heaven say, “Write this: Blessed are the dead who die in the Lord from now on.”“Yes,” says the Spirit, “they will rest from their labor, for their deeds will follow them.”
From Rev 1, we know that the book was to be written, but when?
Rev 14 is time specific because the angel said that people who die in the Lord from that moment on- clearly showing that the application of the blood of the lamb to the end times people started that specific moment that the angel was speaking.
There's no way that book was written 70 years later when the angel was time conscious at that moment of revelation. The disciples and apostles had 3.5 years to work with and by the end of these 3.5 years, all scripture was ready (even though each book separate) as it is today.
I can confidently say that by 38 AD, all scripture were done.