Why does Iowa still need to go first, lol?
South Carolina isn't important because it's in the former confederacy, it's because it's the first proper chance for one of the most important Dem constituency - black people, particularly black women - to have their say instead of just white farmers.
Basically the first four right now are:
Super white tiny state with weird retail politics rituals.
Super white tiny state that doesn't match the US national electorate at all, but is a swing.
Red state that gives black people the first major say in nomination.
Western state with a stupid caucus system, one particularly strong union, lots of migration that makes polling difficult, but the first proper say for Latino voters.