I think you have the causality reversed here. White supremacy did not create enlightenment and democracy, but the ideals of enlightenment and democracy did make white supremacy necessary. The Romans and other slaveholding societies did not think there was anything wrong with enslaving human beings. Slavery was just part of the social order, decreed by God or the Gods, and some people were supposed to be on the bottom, end of story. For the Greeks and Romans, anyone could become a slave if they were captured in war. It didn’t matter what your skin color was, and it didn’t matter how smart you were. It was pretty common for a Roman who couldn’t understand geometry to buy a Greek slave to teach his kids geometry. That Roman obviously recognized that his slave was in some sense smarter than he was, but that raised no moral problems for him.

However, once you see society as a social contract voluntarily entered into by free humans, there’s only one way you can justify slavery. You have to claim that slaves are in some sense not really human. The most effective way of maintaining this illusion is to have all your slaves be a different skin color, and claim that they were biologically and intellectually inferior to people with your skin color. Without the ideals of democracy, slavery doesn’t need to make that claim, and race makes no difference as to whether you should be enslaved or not.

So in short, White Supremacy did not create Democracy, but Democracy did create White Supermacy. White Supremacy is not a stepping stone towards Democracy, but the last stand in the fight against it.