You’re overthinking it.
The north didn’t want to end slavery or punish the south per se. The North had its interests and the south had their interests. Slavery was certainly a part of it, but in the lead up to the war, Northern interests were much more in containing slavery than ending it. The southern interests were heavily against this containment strategy because containing slavery meant restricting a commodity that they had cornered the market on.
Somehow that story doesn’t get told much, history written by the victors I guess, but as northern-aligned states ended their slavery practices, slavers in those areas often sold their slaves to plantation owners in the deep south rather than free them because they didn’t just suddenly get religion about Negroes being people all of a sudden. A freed slave is worth nothing, but a slave who is going to be freed if he stays where he is can still be worth money if he’s sold in a southern slave market.
The North didn’t secede from the South, it was mostly ok with the status quo (and remember that the terms “north” and “south” are only really the political classes and business leaders of each section of the country, most of America in both the north and the south were ignorant to (or disinterested in) what was going on in those days with slavery, and even folks like Lincoln who morally opposed slavery from a young age would be considered quite racist by modern measures.
BOOM! that mic drop just blew some minds open. but only those who still have critical thinking abilities!
there are still far too many kids being indoctrinated by lincoln revisionist / public schools into the " slavery was the only reason discussed in this school, for the U.S. civil war, lincoln was a hero" blind/ no thought education.
Information on how Northern states rid themselves of slavery, over time.
https://en.m.wikipedia.org/wiki/Slavery_in_the_United_States#Abolitionism_in_the_North