Not surprising. Hillary beats Bernie in Republican areas as Bernie’s too radical for those areas
It’s simpler than that. Hillary got the black vote and in the South that is 80%-90%+ of the Dem primary vote.
Probably part of the reason why the superdelegates are for Hillary—they are afraid the black Democrats won’t vote for Sanders in the general because he is Jewish. Come to think of that—could that have suppressed the voter turnout in 2000—that Gore picked a Jew for his running mate? (Of course Gore “won” the popular vote, but just a plurality—he had under 50%.)