This is why I avoid “historical” movies.  First off, however Moses and Ramses looked, they weren’t white.  This is because white people (as in:  people that look like Christian Bale and Joel Edgerton) aren’t native to that region.

Now there were conquests made by Europeans, primarily Alexander the Great, but that was significantly after Moses would had been on the scene.

For instance, Egypt geographically neighbors Nubia.  The two countries were often in conflict–which is why some hieroglyphs contain figures that are darker-pigmented than others.

There was a period though, when Nubia conquered Egypt, and the Nubian rulers adopted the mores of Egypt, ruling that country for a period of time.