When it comes to the civil war, different people are going to give different opinions, about why such a war was fought of which some of those opinions would consist of: the freeing and hence the liberation of all slaves, the re-unification of the union, the invalidity of those that lose at a legitimate democratic election taking up arms, and so on. Each of these is absolutely valid but there is one additional very salient reason why those in the north were so set upon subjugating those in the south and that was for the elimination and annihilation of the southern aristocracy.
Before the civil war commenced, quite obviously all of the States of the union were in the continental United States, but there clearly was a division of economy as well as infrastructure between those located in the north and those located in the south. The north was far more educated, was far more industrialized, had far more railroads as well as canals, had far more cities, along with far more recent European immigrants, and a far higher population than the south. The south was a plantation society, and in particular, a plantation society owned, operated, and controlled by the largest plantation owners, of which, those that were enslaved as well as poor whites were all under the domain of that dominance. The north was a far more egalitarian society and south was one that foundationally was built upon the exploitation of slaves, as well as an underclass of poor illiterate landless whites.
One might think that because the south was made up of one-third of those enslaved, as well as having a massive amount of non-land owning whites, that to even contemplate rebellion against the union, would be absolutely futile along with being quite delusional in the belief of any possible success. However, those wily southern plantation owners in conjunction with their obedient political leaders were able to make the case to their landless white citizens, that the election of Lincoln, would lead to equality between all races, and therefore even the lowly illiterate whites would lose their caste status over blacks, and further that whites would lose their economic edge over blacks by now having to compete against blacks for free labor; in addition to the fear that blacks would run rampart over the honor of white people by raping and violating white women, with absolute impunity.
So many of those that fought so nobly on behalf of the north, looked upon the fight against the south, as the need to tear apart and eradicate once and for all this southern aristocracy, and thereby the elimination of any semblance of that privileged plantation white class from making their living in the reaping of their benefits by the sweat of those so enslaved and those so exploited. This meant that the war of north and south truly was a war to remove the yoke not only from the black man's neck but also from those seen as poor white trash.
In that fight, the north initially appeared successful in accomplishing just that, until the southern aristocracy was able to within a few short years after the civil war, rise again, and pretty much get back to business as usual, leaving blacks and landless whites, pretty much where they were, enslaved by another name, and exploited just the same.