You had politicians in the North, successful ones, including Lincoln and also much of the Republican party, who openly opposed slavery. Why would they do that if they were as apathetic as you claim. It's true that few people believed in full equality. But the notion that people didn't care about abolition is revisionism.
At the time, you had many successful politicians speaking against slavery. Why would they do that if the people they were talking to didn't care?
Yes, they cared, however, the reason they care was economic and social, but not moral, as you presume. I am not saying none had moral objections, many of the transcendental thinker did object to the 'peculiar institution' on moral grounds; these are the ones would read about in elementary history books. The vast majority of people living from 1800 to 1860 cared little about the slave issue, other than not wanting it spread to their territory.
In truth, most common people disliked the presence of Africans more than they disliked slavery. First of all, it gave the slaveholder a labor advantage in procuring land. Secondly, slavery was seen as inferior to the wage system, which omitted the need to care for worker's children and when the became old; it also omitted the need to shelter workers and feed them. In economic terms, the wage system was more economically efficient. In the defeated South where monies were short, many former slaves returned to the same labor as
sharecroppers
See "The Devil’s Punchbowl"; mny former slaves were actually detained by union sholders and left to starve. The Union was not all good Afreican loving persons who wanted to free skaves, and many detested slaves, as well, the notion they had to risk life and limb for people they did see as fully human. What they believed is they were fighting to perserve the union and their country.
You have to realise this was a time when wage laybor was highly exploited, and salvey, as cural as it could be, necessatated a 'keeping and caring for' the means of laybor.
"Leading up to the war, most Northerners did not possess markedly different ideas about race and equality than their Southern opponents did. Absent some grand northern epiphany in the spring of 1861, the idea that the North took up arms over the issue of slavery seems very unlikely."
https://www.thegreatfiction.com/2015/01/05/did-the-north-really-fight-to-end-slavery/
"Even after the commencement of hostilities, Union politicians continued to go out of their way to explain what they were fighting for and, as importantly, what they weren’t. In July, the Crittenden-Johnson Resolution was passed that stated that the North was not fighting with any “purpose of overthrowing or interfering with the…established institutions of those states.” In other words, they weren’t fighting to end slavery, but only “to defend and maintain the supremacy of the Constitution and to preserve the Union.” What the North meant by “the supremacy of the Constitution” would have been an unfamiliar definition to the founding generation.
In order to prevent any additional states from joining the Confederacy, Northern politicians and military officers made a point of not offending slaveholders in the slave states that had not yet seceded. When Union general John C. Fremont used his authority to free slaves in Missouri in August of 1861, Lincoln countermanded his order, sending those slaves back into bondage, and relieved him of his duties. In West Virginia, Union general George McClellan promised slaveholders that he would allow no “interference with your slaves,” and that “not only will we abstain from all such interference, but we will…with an iron hand, crush any attempt at (a slave) insurrection.”
In fact, had the states not been so turn over past political differences, and the war had not occurred, slavery would have died out in less than twenty years. As we have seen in history, many former slaves ended up back working the same plantations, but no longer received the shelter they had under slavery. Many Africans starved after the war, as there was no welfare system at the time.
"
Sick From Freedom, the reality of emancipation during the chaos of war and its bloody aftermath often fell brutally short of that positive image. Instead, freed slaves were often neglected by union soldiers or faced rampant disease, including horrific outbreaks of smallpox and cholera. Many of them simply starved to death."
https://www.theguardian.com/world/2012/jun/16/slavery-starvation-civil-war
"In the 19th century people did not want to talk about it. Some did not care and abolitionists, when they saw so many freed people dying, feared that it proved true what some people said: that slaves were not able to exist on their own," Downs told the Observer."
Powell believes that “The choice wasn’t to fight the Civil War or do nothing meaningful about slavery.” He continues, “We should stop viewing the Civil War as the only way or the best way freedom could have been achieved.” Powell is on to something. Not only did the war decrease the amount of political freedom that all Americans had, but it also contributed to the post-war environment that denied full freedom and equality to the emancipated slaves."
The 'War Between the States' was necessary to make America great then, and as we clearly see, after the war, the US began to complete coast to coast railroads and soon became a dominate and
wealthy nation.