why did congress not agree to lincoln's reconstruction plan?

Answer 1

President Lincoln advocated a moderate plan for Reconstruction of the South but the Radical Republicans did not believe that Lincoln went far enough in punishing the South. Moreover, the Radical Republicans believed that Lincoln did not protect the rights of freeman (former slaves).

This is a complicated event in history and it can't be answered in a couple of lines but I have tried to summarize the best I could in 2 sentences.