The South is a notoriously evangelical region, so it should have gone to Ted Cruz or another candidate who focused more on social/religious issues. Trump was mostly focused on economics in the Upper Midwest, though. Were these voters convinced by racism, or were there other factors involved in their decisions?
Vote-splitting, basically. It was often the case that when the early votes would come in Trump would lead massively, with Rubio in a distant second, and then when the votes on election day came in Cruz would come within single-digits of making up the gap (as he did in LA and MS). It's very clear that he would have lost a straight fight against either man throughout most of the region.
