If you know how Wikipedia works, you have a good idea of how the authorship of biblical books went down: an anonymous text is added to over time, but none of the additions are screaming for individual recognition. Benjamin Sommer explains the phenomenon this way: As Walter Jackson Bate and Harold Bloom have shown, poets since the romantic era [sic] have attempted to cover up the extent to which they are indebted to their predecessors.

Source: the Bible: it’s sort of like a viral internet joke (or, why “original author” is overrated)