“personally, I find the common atheist assertion that "these books were written by man" completely irrational and ahistorical.”
That’s odd, because a common believer defense of anachronisms, contradictions, and errors is that they were fallible men that wrote it, so it doesn’t detract from God’s perfection.
"Who exactly is their author?”
That’s a good question. Nowhere in Matthew, for example, does it actually say ’I’m Matthew and i’m writing this.’ Historians really really like to know who wrote any document, for what purpose, and when. Without that, it’s not much use for ‘history.’
"There's no historical documentation that suggests it, and in many cases, it would require widespread conspiracy to perpetuate the fraud - which also lacks evidence.”
Someone writes down what HE maintains GOD told him about, say, Genesis, or Moses, or Jesus’ Childhood… Why would a conspiracy be necessary?
“Yet atheists continue to insist, utterly without any evidence, that there was some phantom author.”
No, the phantom is that God inspired the men to write this stuff.
“please explain the existence of religious texts and the religious experience of the first generations that experienced those texts”
We don’t know when these texts were written. We don’t have the originals. If you want them to be of divine origin, the burden’s on your dumb ass to back it up.