Why Were The Radical Republicans Radical?

[My Name Is Kate]

Why were the southern states so afraid that Lincoln was determined to abolish slavery, that some of them immediately seceded from the Union when he was elected, when he stated in his first inaugural speech that he had no intention of doing so, and did not even have the constitutional right to do so? Why didn't they trust him?

If the South hadn't seceded, and if the Civil War could have been delayed until after the mechanical cotton picker was invented and there was less need for slaves, would slavery likely have died a natural death, and the war been avoided altogether?