Actual ancient historians will look at sites, and based on the evidence found, come up with plausible theories to explain what transpired. These theories are based partly on the evidence, and partly on what we know about other events and sites from around the same timeframe.
Graeber, Harrari, and others take these theories, inject their personal biases, and present them as facts. For example:
> What this new evidence shows is that a surprising number of the world’s earliest cities were organized along robustly egalitarian lines. In some regions, we now know, urban populations governed themselves for centuries without any indication of the temples and palaces that would later emerge; in others, temples and palaces never emerged at all, and there is simply no evidence of a class of administrators or any other sort of ruling stratum.
Notice how he took a lack of evidence of temples and palaces, and proceeded to say that the cities were egalitarian. Based on what? What if those societies had temples structured differently than what you would expect, or if their temples were destroyed by outside invaders? And beyond that, there is an implied claim that you either have temples, or you are egalitarian, with no mix in between.
This level of non-scholarship reminds me of the Calvin and Hobbes bit where Calvin claimed that "bats are bugs" and proceeded to write up an entire school essay on the topic.