Actually, if you think about it, it makes perfect sense. If the Nile basin was suitable for human habitation, Egypt or other North African civilizations would have moved south long ago. From the distribution map of the Arabian Sect in Africa, it's clear that they actually have more frequent exchanges with West Africa, where there are a bunch of Black countries and tribes that believe in the Arabian Sect. This further proves the harsh environment at the junction of East and North Africa.
Of course, besides the climate factor, the indigenous people of ancient Africa were not as easy to bully as imagined. At least in the era of cold weapons, the relatively backward Black people could still stand against the Arabian civilization of North Africa.
In the region of the Nile River Province in East Africa, the areas with better economic development are precisely in the northern desert region. As for the south, apart from a few cities, there are basically not many people.
