Really?? The only 'proof' is some obscure historical document that may or may not be accurate. I doubt modern Christians even have the authors right. They certainly don't when it comes to the Gospel of John. The other 3 would be written by Peter (Matthew) James for Mark and the later book bearing his name and his brother John wrote Luke.
The Disciples that came to take away Paul's blindness were gathered after the cross, the cross was the only thing that stood in the way of the Scribes writing the books as that was to be done with some assistance from the Holy Spirit.
What Peter talked about to the Gentiles after Acts:10 is the same message he would have talked to the Jews about during the 30 years it took for Luke:21:12-24 to be fulfilled. That is the same message Saul was delivering to the Gentiles in his visits.
I suppose the Luke:21:12-24 prophecy was written in hindsight as it was referencing 70AD in it's last verse. I think not. James starts out mentioning the scattering and that did not take place until 70AD so that book was not written before then and it references a prophecy from De:4:30. The point of the Gospels is they were written by Jewish people but the writing was in Greek, perfect Greek and that should not have been possible as the Jews never had any contact with any Gentiles until more than 3 1/2 years after the cross.
If you can mistake the concept of these verses then the rest of your doctrine will be even more flawed.
Joh:21:24:
This is the disciple which testifieth of these things,
and wrote these things:
and we know that his testimony is true.
1Jo:1:1-3:
That which was
from the beginning,
which we have heard,
which we have seen with our eyes,
which we have looked upon,
and our hands have handled,
of the Word of life;
(For the life was manifested,
and we have seen it,
and bear witness,
and shew unto you that eternal life,
which was with the Father,
and was manifested unto us

That which we have seen and heard declare we unto you,
that ye also may have fellowship with us:
and truly our fellowship is with the Father,
and with his Son Jesus Christ.
If you don't want the book to be viewed as being 'divine' then you have to muddy such things. 3 Apostles see 3 events and today the 3 books that cover those events is attributed to anybody but those same 3 Apostles. That is equal to putting in overtime.