Final answer:
The fall of Nubia/Kush was not caused by being taken over by Assyrians or the kingdom of Aksum. Factors that contributed to their downfall included environmental factors leading to a decline in agricultural productivity and the weakening of the Roman Empire's economy.
Step-by-step explanation:
The fall of Nubia/Kush was not caused by them being taken over by the Assyrians or the kingdom of Aksum, as those were indeed factors that contributed to their downfall.
One reason for the fall of Nubia/Kush was their inability to produce enough food. This was a result of environmental factors such as aridity and soil erosion, which led to a decline in agricultural productivity.
Another reason for their decline was the weakening of the Roman Empire and the contraction of its economy, which resulted in a decline in demand for Nubian luxury goods.