How did northern interests present problems for the reconstruction efforts?

Northerners had many politicians that didn't essentially care about reconstruction or African-Americans. They just went south to get into positions of power because the political area was open for newcomers since the old politicians in the South were the racists who led to the war. As they weren't that interested, the ideas of democracy soon ended and the policy of separate but equal was established which still enabled racism and segregation only in a legal manner.