If the concept of peaceful secession was "never in play" it was because Lincoln said he would never allow it in the first place. The South prepared for a fight because Lincoln said he was going to bring them one. This despite the fact that the Constitution does not prohibit the States from secession nor does it grant the Fed govt the power to prohibit it. Still, you have not answered the question of why peaceful secession would constitute "insurrection" when nothing in the Constitution prohibits it and the Constitution specifically reserves for the States all powers not specifically delegated to the Fed?
Henry Clay's compromise of 1850 is credited with averting civil war, and for holding the Union together.
Given that Lincoln wasn't elected until 10 years later, one cannot blame him for the violence. It was probably inevitable.