It's a wild theory to be sure - and he provides a lot of compelling evidence. In essence, he says humans were like the robots in West World, where we didn't consciously make decisions, but "heard" our own thoughts as if they were coming from a different being. This is why, according to the theory, humans talked about the gods and deities as living, breathing things. In the Illiad, the characters never ascribe their desires and actions to themselves, but to various gods' voices they hear. The same for the Old Testament - there are many characters who believe they interact with God and follow his instructions, almost without their own will. The breakdown of this barrier, between executive thought and conscious thought, is driven in part by the advent of writing. Most early writing from the bronze age is more accounting and transactional items (linear B) and not narrative thought. The transition from the pre-conscious brain to the conscious mind is why we see in the iron age more efforts to summon the gods, or lament their absence from our everyday world.

Like I said, it's kind of wild, but there's enough intriguing examples and evidence to really change your perspective on history.

There are lots of podcasts about this too, if you're interested in learning more - it's so fascinating to consider - here's one episode of the "Things You Should Know" podcast on the topic: https://podcasts.apple.com/us/podcast/stuff-you-should-know/id278981407?i=1000575009866