This is really interesting. It’s two-parts, but I’m not posting both to prevent clogging dashboards.
If you do not believe that this is actually what happened, I suggest reading up on the Documentary Hypothesis about the authors and what they contributed/wrote, and then reading up about the Dead Sea Scrolls. This is quoting the Oxford Companion to Archaeology
The biblical manuscripts from Qumran which include at least fragments from every book of the Old Testament, except perhaps for the Book of Esther, provide a far older cross section of scriptural tradition than that available to scholars before. While some of the Qumran biblical manuscripts are nearly identical to the Masoretic, or traditional, Hebrew text of the Old Testament, some manuscripts of the books of Exodus and Samuel found in Cave Four exhibit dramatic differences in both language and content. In their astonishing range of textual variants, the Qumran biblical discoveries have prompted scholars to reconsider the once-accepted theories of the development of the modern biblical text from only three manuscript families: of the Masoretic text, of the Hebrew original of the Septuagint, and of the Samaritan Pentateuch. It is now becoming increasingly clear that the Old Testament scripture was extremely fluid until its canonization around 100 AD
(Fagan, Brian M., and Charlotte Beck, The Oxford Companion to Archeology, entry on the “Dead sea scrolls”, Oxford University Press, 1996.)