But this is what we do know
1 the authors intended to write realiable documents.
2 the authors had access to realiable sources
What is your evidence?
Why is the bible true and not the Mahabharata? You have a guy narrating a story who had been given divine sight, which was a refreshing acknowledgement of the problem that he couldn't witness the things he discussed. The bible rarely even has that. The Holy Spirit gave them Google Translate or something. It didn't give them knowledge. You also have the very real problem that if we take the bible as true, then it is also true that people are liars because it says so, and people wrote the stories. Saying God inspired them is meaningless because they wrote themselves out of credibility. Jesus thought they were losers who didn't understand him. How can we trust their take on things, then? Why would the authors have different takes on how things went down if the Holy Spirit dictated the truth to them? It's not like one author focused on the economy, one focused on religion, one focused on politics, etc. They attempted to tell the same story 4 times, and they can't get it straight.
We know that the authors where honestly trying to report what really happened because the gospels are fool of embarasing details that nobody would invent + the fact that the gospels have the same style as Greko- Roman biographies. Legends, myths, poems had different styles.
On the contrary. Each disciple supposedly had a following. Those followers didn't agree with one another. Thus, they come off as trolls:
Author A: I am a disciple of James. Peter sucks. I'm going to go to lengths to show just what kind of a failure he was.
Author B: I am a disciple of Peter. Peter ... Peter ... I mean, everyone pretty much agrees on Peter. However, I'm going write that he repented of his evil betrayals and personality flaws even though he dies having never really changed much.
Author C: I am a disciple of John. John couldn't bear the loss of his "special friend". I will write about how much Jesus loved John while trying not to make them sound gay.
It's like watching the news, where what is reported depends on who pays them to talk.
The reason why we know that the authors had access to reliable sources is because the gospels are correct in a multitude of geografical, political, demografic, historical etc. Details. Only someone with access to proper sources would have known all those details.
You keep saying that, but you also enjoy ignoring all the places where it gets things wrong, like anachronisms. The stories were told to give meaning to the current events happening in the authors' lives, which is why you see verses like "and so it is to this day". People who are witnessing it don't say that, because it IS that day for them.
Let's say you are watching the news. Several planes have caused deaths and structural damage. You get reports about terrorists, a government conspiracy, faked video, etc. What fascinates me is that people can say "yeah, but that is 'fake news'", but when the bible does the exact same thing, it's "it must all be true."
It's like politicians: we know politicians are lying when their mouths are open. However, biblical and essentially mythical versions of the founding fathers of our own country were totally never just spewing stuff to make the population quiet. No, they must be telling the truth, because I am gullible enough to swallow propaganda.
The Old Testament is a fight of propaganda between pro-monarchy and anti-monarchy people. Every book relates to that fight, because as the bible notes, King Josiah only "discovered" (coughcough) a law book, which means every other book up to that point must have been written at least during his reign if not later, which ALSO means it is a propaganda war between both sides in the monarchy debate. Moses is torn between being portrayed as a great religious (non-king) leader and a strong military leader (which is what the kings would've focused on).
The New Testament is a fight of propaganda between Jews and gentiles. What really happened is irrelevant, because it's about "We Jews are the Chosen Ones" and "Nuh-uh, we gentiles are the Chosen Ones" and "Uh-huh, nuh-uh, uh-huh, nuh-uh." The reality is that the books are written after gentiles start to be included after mostly Jewish rebuttal, so the plots reflect where the authors stand in relation to that debate.
Only someone with access to proper sources would have known all those details.
Are you telling me that if I watch a play-through of Five Nights at Freddy's, a horror game about rogue animatronics possessed by victims of a serial child killer, the fact the plot has an insane amount of detailed backstory means the author of the game must have witnessed this?
If I ask you to invent a story about a guy who lived in jerusalem 40 years ago
You would be called out, because he lived in Galilee, not Jerusalem. YOU can't even get the details right.
But the author of Spiderman does not intend to write historical events.
1000 years from now, how will this be determined?