What three events or trends that led to the collapse of Reconstruction in the South after the Civil War and why?

There were several events that led to the collapse of Reconstruction in the South. The first was the weakening and eventual end of the Freedman's' Bureau, which had acted as an advocate for the newly freed slaves on many levels. Next, was a weak president, Andrew Johnson, who appeased the former Confederate states by removing federal military districts. Another reason was the shift from the Radical Republican representation in Congress, to the Liberal/Republican party who were not as interested the plight of the newly freed slaves.