I really like the idea that this concept of spiritual devolution is picked up so easily by us here.
But I would like to say that even the need for oral traditions was already on that path of spiritual devolution. There is a time before oral traditions, and my suggestion is that in those days we had full capability.
So what happened that we suddenly needed to express the then obvious into symbols?
That later on people started to misinterpret those powerful, original symbols is yet another few steps down the spiritual devolution ladder.
Maybe even the AE had only a limited understanding of the original full meaning of the precessor of what they called Osiris.