It's probably because none of the New Atheist celebrities and atheist podcast stars were historians. They were philosophers, biologists, political commentators, podcasters.Agreed. What's weird is the militant atheists only use that line of argument for the Bible, not other historical writings from other religions and cultures. Weird!
Therefore they wouldn't have actually realized they were selectively applying a hyper-skeptical standard to the Bible that they never apply to other quasi-historical writings from antiquity.