Second, to be more accurate about it, the brutal conquest of the south by the likes of 'pyromaniac' Sherman and his thugs combined with the the subsequent rape of the south by the carpetbaggers and thieir associates turned the south into solid Democrat for nearly a century.
Yes, but that doesn't entirely explain why the South decided to go with the Democrats. That part can then be explained by noting that the commander-in-chief during the war was a Republican. Had Abraham Lincoln been a Democrat, we would have seen the solid Republican South.
And sure, technically speaking Andrew Johnson was not a Republican, but he was on a ticket with Abraham Lincoln. I don't think many Southerners would have cared about anything else; that's enough association with the Republican Party for them right there.