Aren't you doing the same? You presume when Moses originally wrote Genesis but you present no evidence for them.
(See my signature?)
I am not presuming anything; I am iterating what known traditions about Genesis being spread by Abrahamic religions.
According to traditions, both Jewish and Christian traditions, Moses was said to be author of Genesis.
And though I am iterating these traditions, I am also skeptical of such traditions, because I no longer believe in these traditions that accept Moses as the author of Genesis, or of Exodus, Numbers and Leviticus.
When authorship are in doubt, then I would not call Moses an “author”; instead Moses has been “attributed” to be the author.
And even when books are titled by names of prophets, it doesn’t mean they were authors of the books.
The other problem is that there are no Bronze Age sources. No writings of the Bible in any shape or form (eg clay or stone tablets, parchments, papyri, etc) exist in this period. There are no original Bronze Age Genesis or Exodus; all evidences of biblical texts, only exist from Iron Age period, from King Josiah to the early Second Temple period.
Take for instance, the Song Of Songs for instance. The book has no names in the book, but because for centuries, respective Jewish and Christian traditions have attributed the Song to King Solomon as its author, Solomon’s authorship have become accepted by the evangelist and orthodox churches, even though Solomon couldn’t have written it.
Studies in the linguistics have demonstrably shown that the vocabulary, idioms and syntax used in Song to be composed originally in Aramaic language, not Hebrew. That would indicate Song was written much later than Solomon.
In the New Testament, none of the named evangelists are the actual authors of the respective gospels. The gospels were actually written anonymously, and it wasn’t until 2nd century CE that church traditions ascribed the names to these gospels.
As to the epistles that have been attributed to Paul, less than half of them were authentic Paul’s authorship. The rest of epistles are in doubts.