There is an assumption that King Tut was of the same ethnicity as the Egyptians he ruled. Cleopatra and Ptolemy (despite the afro-centrists beliefs) were Greek -- after Alexander the Great conquered Egypt, he installed a new Macedonian ruling class. During the period around 2000BC to 1550BC the Hyksos from (apparently) western Asia (Middle East) invaded and ruled Egypt. So the genetics of the ruling class may not be representative of the common people.
Well Tut’s dynasty lasted for quite some time. It’s possible that the people who ruled Egypt by the third dynasty were not the same as the people who ruled in the 1st and 2nd.
However, the origins of Tut and his family could be explained if they had Assyrian ancestry and Thutmose I married into the existing Egyptian royal family.
However, that still doesn’t change the enormous population dislocation of the end of the Roman Empire.