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I think you'd like Why We Keep Asking “Was Machiavelli an Atheist?”, about how really hard and slow the path to atheism was.
However, I don't think it took atheism to get to "the map is not the territory". I think it's just difficult for people to realize that their thoughts are a very incomplete description of the world-- the stuff in your head feels so plausible.
Why do you think it was not necessary for it? To me it is the discovery vs. invention problem. With theism truths are made by discovery, truth is the information that is closest to the priomordial information of the thoughts of the creator, the primordial blueprint. Without theism, truths are simply models, tools, handy little gadgets used for prediction and invented, not discovered.