Your logic does not hold.
The north went to war to secure a tier of states it could continue to treat as a second-class source of raw materials for its own mill industry. Threats to end slavery were threats of economic sanctions. Tariffs were designed to force trade with the North and hamper industrialization in the South to preserve the status quo. The cause was economic in nature.
False altruism might make for nice fairy tales, but it was all about the money.
Slavery depended on new land, because slaves had to be kept ignorant to remain slaves. Old farms became unprofitable except as a place to breed slaves. Example: Arlington Va.
Closing the territories to slavery would have killed slavery, by reducing demand for slaves, dropping the price.
The south started the war, and attempted to invade the territories, to the extent they could. They had tried to start the war in Kansas, in an attempt to corruptly install a slave constitution. They were stopped. They started the war at Ft. Sumter to induce Virginia to join their insurrection.
Actually the logic is self-evident.
Lincoln said that although he would resist the expansion of slavery into the territories he understood that (irrespective of his feelings regarding the institution) slavery was sanctioned by the constitution. His stated intention was to maintain the union as it was.
The notion that anyone sought to “secure a tier of states” is utter nonsense. The idea that the souths’ failure to industrialize was founded in anything other than sloth is ludicrous. “The cause was economic in nature.” Yes - the economics of slave labor.
I agree, but then what role did the Republican abolitionists and Lincoln play? Were they useful idiots for the power brokers that wanted to game to continue to be played, or were they a part of the conspiracy?