Reconstruction would have succeeded if Lincoln hadn't picked a vice president that was a known confederate sympathizer in the name of bOtH SiDeS MuSt UNitE. If Lincoln hadn't been shot, or if we'd had a Grant or Sherman presidency immediately after Lincoln instead of Johnson, we wouldn't have had Jim Crow or had to deal with "But mUh HerRitAge" morons.

The myth of the lost cause and pretty much the entire rightward shift of the south was a systematic effort by confederates and their sympathizers (translation: traitors and traitors with extra steps) to undermine the northern victory by painting their literal actual treason as somehow the heroic act.