"States' rights" only in the sense of some states' rights to unilaterally declare secession, form their own Confederacy, then provoke, start and formally declare war on the United States while sending their own military to support Confederates in Union states & territories -- yes, indeed, those "states' rights".
In fact, secessionists of the time, 1860 & early 1861, made no secret of their primary purpose, to protect their "way of life" and their "peculiar institution", slavery, against Northern abolitionists and "Black Republicans" like Abraham Lincoln.
Those secessionists were not ashamed of slavery, far from it, they were quite proud, saying slavery was the greatest wealth-producing invention of all time.
Because of slavery, the average Southerner was better-off than average northerners, and the wealthiest individuals in the country were the great Southern plantation owners.
So Deep-South secessionists could not imagine living without slavery, and took as total "fighting words" any call to restrict, much less abolish, it.
That's why the mere November 1860 election of "Black Republican" Lincoln was so unacceptable that secessionists immediately began organizing to declare independence and form their own Confederacy.
It was all about protecting their "peculiar institution" of slavery.
Of course, neither slaves, nor slavery started Civil War -- that was done by secessionists eager to assert their ownership over anything Union within slave-holding states.
“Because of slavery, the average Southerner was better-off than average northerners,”
The average southerner didn’t own slaves because they were too expensive. The majority of slaves were owned by a very finite number of people. Northerners also owned slaves including officers in the Union army.
The slavery issue and abolition were pushed to gin up northern support for a war agains’t the seceding states. Most Northerners were not that interested in the issue and most did not support a war.
I will have to question that one. By the 1860s, the industrialists of the North were already amassing huge fortunes, such as the Vanderbilts, who were building a railroad empire.
The wealth of the plantation owners of the South was greatly overstated due to the free labor they enjoyed. Everything was done for them for free and all they had to do was sit on the veranda and have refreshments brought to them so they could certainly have the appearance of being very wealthy. But in reality, they created very little wealth. Which was why when slavery was abolished, the South instantly became the poorest region in the country and even to this day, there are pockets of poverty that go back to Civil War days.
As the Industrial Age boomed after Reconstruction, nearly all the great fortunes were made north of the Mason-Dixon line. The white Southerners as a whole had no work ethic. They considered menial work "demeaning" because up to that point, only slaves had been asked to do it.
People of the North had no issue rolling up their sleeves and being industrious. People of the North were derided by Southerners as "mechanics" and "city slickers" but they were were mostly the ones that turned the United States into an economic juggernaut and the envy of the entire world.
I know that does not fit with what some may want to believe but there it is.