There was absolutely no reason for Southern plantation owners to move North with their slaves, and they had no inclination to do so. There was also evidence that slaveholders would not migrate into the Territories.
However, they were actually demanding the preservation of equal guarantees of application of federal laws.
Slavery was dying in the rest of the world. It had little chance of spreading further into new territories of the continent. If slavery spread, then it would take the slaves out of the United States.;
Slavery had reached the limits imposed on its expansion by geography and crop climate as Kansas, New Mexico, and Utah amply showed.
The census of 1860 verified this and revealed that there were precisely two slaves in Kansas, and only a handful more in all the remaining territories.
Slavery was not a genuine issue and there was no need to go to war over it. The men of 1860-1 allowed an academic argument about an imaginary slave in an impossible place to end in a bloody civil war.
If the question was merely one of slavery in the territories, then competent political leadership would have been able to cope with it.
Instead, the Northern political class, seeing that the South was steadily becoming a minority in the United States, remained frustrated at the South's ability to cling to power. Not only was the Northern stand against the threat of slavery in the territories an act , but Northern expressions of moral repugnance towards slavery were just hypocritical self-serving grandstanding.
I do not believe one word of this entire post. It is a peculiar version of one of the most studied periods in human history. You may be looking through the wrong end of the telescope. You certainly have a uniquely one-sided perspective.