Several factors might influence the popularity between Egypt and the Kush kingdoms; one of the factors could have been that Egypt was forged before, and it's considered pioneer on that territory until the Kush kingdom conquered later, by the way Kush and Nubia are basically different names for the same thing, referring to the same region at south Egypt and what is Sudan nowadays. They started as the Kush kingdom and when they conquered Egypt people called it Nubia due they were under Nubians rulers.
Another factor affecting its popularity could have been misogyny in modern times due Kush/Nubia was mostly ruled by queens, and Egypt was mostly patriarchal.
And another factor could have been that Kush/Nubia rulers adopted themselves and encouraged sort of an Egyptian style type of culture, even building temples honoring Egyptian gods.