Answer:
Kush declined because of overgrazing of the land and overuse of the forest, so no more wood, so no more iron weapon making.
Explanation:
To begin with, it was because the Egyptians dreaded the development and new intensity of the Kush. At that point, they took over Kush. At last, Egypt's capacity declined, and Kush recovered their territory, yet a significant part of the Egyptian culture remained.
Loss of assets enabled cows to overgraze the land. With no grass, there was nothing left to hold the dirt set up, and it overwhelmed. Likewise, iron producers spent the woodland on wood. So no weapons could be made, or merchandise exchanged. The military went downhill.
