Stalin was a Georgian running a Russian Communist Empire (he appealed to Russian patriotism in WW2 , with reference to Russian heroes like Nevsky, Suvorov, etc) . First proof of diversity.

And the USA is still run by one race and gender. Look at their President and Cabinet. Most of them belong to the same race and gender as 30 percent of the population. Even Obama is half of that race. He wasn't fully from the other race or gender.

Let's take the Ottoman Empire as an example. The Janissaries were Christian children from the Balkans who were converted to Islam. They were the stormtroopers of the empire. Most of the traders were Greek or Armenian. The poets were Persian. The Viziers were usually non Turks.