I didn't understand your first sentence?
There's the gospel according to john, which is the fourth, and non-synoptic, canonical gospel. It's what you get when you take a Hebraic metaphysical worldview and try your damned best to cram it into the heads of hellenestic (neo)platonists, which accounts for the whole Logos thing, etc. And even when trying to speak neoplatonist, the author(s) of john can't resist falling back on revelatory rhetoric.
There's the revelation to john, which i, at least, (as a preterist) think is a survival guide to not getting crucified more than anything else.
and then there's https://en.wikipedia.org/wiki/Mandaean_Book_of_John , which i don't know anything about at all. If it does structure itself like a proof, i'd be very surprised.
anyway, my point is that you and i think of “proof” from an implicit or explicit metaphysical background that simply did not exist in the first century.
Far more important to the authors of the constituent works that are now codified into bibles was an exploration of the nature of god, and what that should tell us about how to live well, simply given as an axiom that god exists (or, that god is that by which existence is itself able to be, but let’s not get too fancy!)
Genesis, for example, is not really concerned about “how” the world came to be; it is very, very concerned with grappling with what the right ways to participate in creation are.