Lincoln's approach to uniting the nation was to work towards compromise, valuing Reconstruction over constructing an ideal nation, a nation in which the confederacy and certain elements of southern lifestyle was entirely eliminated. Part of his approach was to set terms for confederate states who seceded to rejoin the union, and these terms were considered too lenient by Radical Republicans. The Radical Republicans were a group that wanted the southern culture to be eradicated, and they did not support that Lincoln was looking to stop the war and return the country to it's previous state, rather than "improve" it. Lincoln chose to implement the Ten Percent Plan, which gave the confederate states good reason to rejoin the Union. The Radical Republicans disagreed with this mercy, and thought that the states should be punished and force to yield to the Union.
Answer: He was viewed as too lenient.
hope this helps!
