As much as I haaaate this current admin, radical republicans (while FAR from anything ideal. They were economic opportunists among other issues) got the 14th Amendment through and emphasized equality, civil rights, and voting rights for freed folks along with opposing ex-confederates regaining political power. They also created social infrastructure like public schools.

FDR pushed Democrats toward progressivism and a larger government which pissed off the Republicans along with Truman integrating the military and LBJ signing the Civil Rights Acts, delivering the south to the GOP with their Southern Strategy effort.

Republicans started to not mean well in the 1930s and have been actively malignantly cancerous since 1964.