It is one of the many arguments that helped Nazism take root. "We were once the great Aryans, but with so many immigrant subhumans and control by the lesser races, we will drown, we need to be rid of them to Make America Great Again, I mean, Rebuild Mother Russia, I mean, bring forth the Third Reich.

https://encyclopedia.ushmm.org/content/en/article/nazi-racism

Plus, it denies the achievements that many groups have made, and pins them upon this supposed master race, painting everyone outside of the race as dumb idiots who needed to be trained and unable to discover things and progress. And dumb enough to be able to either write or have any oral tradition about them, when many ancient cultures had intricate writing systems, and rich oral traditions spanning back to the era when the megafauna was still roaming.