Besides, had that been The Lincoln's only promise, no better way to prevent slavery in the territories existed than to allow the south to voluntarily cut itself away from those very same territories.
And how long before the slaveocrats started uprisings in California, Oregon, Utah, and New Mexico territories just as they had done in Maryland, Missouri and Kentuckey? The record is clear. They did attempt local uprisings in every one of the Western states and territories. They were totally committed to expanding their slave empire through any means possible. They openly boased about their intention to invade Mexico and annex Cuba.
For you to claim that it was somehow tariffs that caused the secession movement while denying that expansion was what drove the confederacy shows either ignorance or self delusion. I know you are not ignorant.
California and Oregon were states, not territories. So were Maryland, Missouri and Kentucky. Those last three especially had large numbers of secessionists, including among them many elected officials, who wanted to join the confederacy. It is therefore absurd to suggest that the confederacy came in and tried to make them unwilling participants. If nothing else, Abe Lincoln held many of the people of these states unwillingly in the union by use of unconstitutional arrests, military force, and disruption of their local governments. New Mexico seceded on its own after The Lincoln's government virtually abandoned them. The confederates were actually very reluctant to take them in, but eventually did so when they offered to help in the war.