“Slavery could have ended peaceably”
That is just not reasonable. Again, in S Carolina, 1/3 of the residents owned 2/3 of the residents, political power would never ever have changed hands peacefully.
In fact the strife to this day of that political change continues 150+ years later.
The northern farmers I descended from knew little of any other issue than slavery. When Fort Sumter was fired upon, there were mass enlistments within days in both Iowa and Wisconsin, that included my family.
In fact, the Iowa militias organized so fast without waiting for a federal call to arms, that they outfitted themselves at their own expense in gray uniforms, unaware the Confederates had picked that color and ignorant that their own federal army wore blue.
And then they had to wait to enter the fight until blue uniforms could be obtained. The early Iowa regiments were state and personally financed.
My family helped many slaves escape to the north and still talked about the danger of the slave hunters around the area. Slavery was a big issue, especially around the Methodists.
“That (Slavery could have ended peaceably) is just not reasonable.”
Why not? The United States constitution provides an amendment process - a peaceful one.