The South voted against Republicans for 100 years after the Republicans covered themselves in chit in the mid 19th century. The South didn't turn conservative. It always was. The Democrats turned from the party of small government, states rights and the working man to the party of centralized power, big government, socialism and most recently fascism....ie government and big business in bed together.
The Democrats turned that way in 1896, and the South was still voting for them up until 1980. Reagan barely won some Southern States.
Fascism is how the civil war started. The protectionist laws passed by congress were meant to benefit primarily Northern businesses. Business became very interested in colluding with government for their own profit, and let us not forget Lincoln was a corporate railroad lawyer, which meant he had worked for the most powerful corporations in existence at the time.
He delivered to them handsomely when he signed the Railways act of 1862, which vastly increased their wealth.
I think Fascism has been baked into our cake since Alexander Hamilton proposed making laws specifically to benefit businesses. The South took the Jeffersonian approach.