It still returns to my original point, that for the vast majority of the rise of Egypt as a civilization, the Nile provided an annual flood, which was followed by a single harvest.
This necessitated food storage for the rest of the year, but if it was a successful harvest, also meant that the rest of the year could be used for other things.
However, if in the early part of their rise, there was warmer, wetter conditions, caused by global warming, it might have given them a smaller, secondary growing season, and a food surplus that could be sold, bringing in great wealth.
Yet with the onset of cooler weather, there would be no extra rainfall, and the land outside of the Nile flood region would dry out.
“By 7,000 years ago (5000 B.C.) and lasting for about four millenniums, the earth was warmer than today, perhaps by 4 degrees Fahrenheit... Although the climate cooled a bit after 3000 B.C., it stayed relatively warmer than the modern world until sometime after 1000 B.C., when chilly temperatures became more common.” - Stanford
This is a bigger point that I'm making than you realize. If you look at the Sphinx, the base of it has WATER erosion, not wind erosion. At that time, the Nile Valley was surrounded by a mesic savannah. The desertification that commenced soon after the Nile Valley civilization began was, in my opinion, the result of the people of the valley assimilating the shepherd culture of the Sahel savannah thereabout. It was that demographic shift from pastoral to agro-urban culture that made Egypt what it became.
That's historic my FRiend. More I can't tell you until I publish.
I'll get to cause and effect when I publish.