1)
There was already a Nevu'ah about the destruction of Egypt! What does this add?
1.
Malbim: Now it explains how the multitudes of Egypt will be cut off. It will be from Hashem, via Nebuchadnetzar. Regarding Kush it was via Mal'achim, and merely to terrify them; they will not destroy the land. Nebuchadnetzar himself will eradicate the multitudes of Egypt, and he will bring with him tyrants of Goyim to destroy the land, not merely to terrify!
