Why did congress think that Lincoln and reconstruction plan was too lenient?

Congress believed Lincoln's Reconstruction plan was too lenient because it aimed for a relatively quick reintegration of Southern states with minimal conditions. His approach, which included the Ten Percent Plan, allowed states to rejoin the Union once 10% of their voters swore allegiance, which many lawmakers felt did not sufficiently punish the Confederacy or protect the rights of freed slaves. They feared this leniency would undermine the federal government's authority and fail to secure lasting change in the South. As a result, Congress sought to implement a more rigorous plan that would ensure civil rights and reconstruction efforts were more firmly established.