Who said the Northern States were fighting to abolish slavery in 1861? Not me! Lincoln’s purpose was to preserve the Union. He famously said so himself:
“My paramount object in this struggle is to save the Union, and is not either to save or to destroy slavery. If I could save the Union without freeing any slave I would do it, and if I could save it by freeing all the slaves I would do it; and if I could save it by freeing some and leaving others alone I would also do that.”
Again, the issue is what drove Southern secession. It was Johnny Reb who started the war, not Uncle Sam. And Secesh was not thinking straight. But the prospect of abolition within the nation’s borders was not the only thing on hisr fevered mind. They dreamed of a Caribbean expansion to build a bigger slave empire.
https://academic.oup.com/jah/article-abstract/61/3/781/703349?redirectedFrom=PDF
By what right did he have to force people to live under his rule who did not wish to do so? The nation was founded on the principle that people had a right to leave the United Kingdom, and that this right was given by God, and so why didn't this same foundational principle apply to anyone who was unhappy with their governance?
Lincoln himself endorsed this principle until it was applied to his government.
Any people anywhere, being inclined and having the power, have the right to rise up, and shake off the existing government, and form a new one that suits them better. This is a most valuable,– most sacred right–a right, which we hope and believe, is to liberate the world. Nor is this right confined to cases in which the whole people of an existing government, may choose to exercise it. Any portion of such people that can, may revolutionize, and make their own, of so much of the teritory as they inhabit. More than this, a majority of any portion of such people may revolutionize, putting down a minority, intermingled with, or near about them, who may oppose their movement. Such minority, was precisely the case, of the tories of our own revolution.Abraham Lincoln, January 12, 1848
And lest you think this was a momentary brain-fart by Lincoln, He did it again in 1852.
Resolved, 1. That it is the right of any people, sufficiently numerous for national independence, to throw off, to revolutionize, their existing form of government, and to establish such other in its stead as they may choose.Abraham Lincoln, January 9, 1852
So Lincoln believed in this right to independence, before he believed in repressing people's independence. He was "for it before he was against it."
It was Johnny Reb who started the war, not Uncle Sam.
Yes, they wanted to keep more of the money they produced, and they wanted to take the European trade away from New York, and the New York Plutocrats who had backed Lincoln were not going to have it.
They should have just kept paying their owners in the North instead of trying to get free of them.