First, the North blamed the South for starting the Civil War, and there was a desire to punish the South for its treason. Second, the North wanted to make sure that the South would never be able to secede again, and so it imposed harsh terms on the South, such as requiring it to ratify the Thirteenth, Fourteenth, and Fifteenth Amendments, which abolished slavery, granted citizenship to African Americans, and gave African American men the right to vote. Third, many Northerners believed that the South was backward and needed to be modernized, and so they tried to impose Northern values and institutions on the South. Fourth, there was a great deal of racial prejudice against African Americans in the North, and many Northerners did not want to see African Americans given equal rights. Finally, the Reconstruction governments in the South were often corrupt and inefficient, which further soured Northern opinion of the South.
As a result of these factors, the South did not receive sympathetic treatment in Reconstruction. The South was forced to make many changes, and it took many years for the South to recover from the war and Reconstruction.