[Genoa]

Slavery was a collateral factor. The sectional conflict was basically about whether the Northern business interest or the Southern agrarian interest would control the policy of the federal government. It had been a simmering conflict for decades. The extension of slavery and slavery itself were the occasion but not the underlying cause. Northerners were no less “racist” than southerners, but slavery meant power, economically and politically, for the South.

[Genoa]

I should add that the North had been punishing the South for decades with tariffs that favored the manufacturers over the growers.

[quadrant]

Grant always believed the admission of Texas into the Union was the major cause of the War, for it is impossible to imagine the South as a cultural, political, social, and economic unit without Texas. With Texas, the South is quite viable; but without that huge land mass, the South has no real substance.
And it is important to remember that whatever the status of slavery, Lincoln could not allow the South to leave the Union and for one reason: no US president - esp one from Illinois - could ever allow the port of New Orleans and the mouth of the Mississippi River to be controlled by a foreign power.

[Lizavetta]

Northerners were no less “racist” than southerners,

When blacks began moving northward looking for work, weren't there quite a few violent episodes of white on black riots?

[BroJoeK]

Genoa: "The sectional conflict was basically about whether the Northern business interest or the Southern agrarian interest would control the policy of the federal government.
It had been a simmering conflict for decades."

But all of that was "politics as usual" for our young republic -- tariffs rose & fell, economic conditions worsened or improved, it all happened within the limits of normal politics.

So, what was new -- what changed in the 1860 Presidential election -- was the first ever officially anti-slavery political party and president elected.
And even as milk-toast & mild-mannered as Republicans then (and now) were, still their opposition to slavery's expansion was enough to convince Deep South Fire Eaters to declare secession, Confederacy and war on the United States.

So for you to say, "Southern business interests" is just a euphemism for protecting slavery, the real reason, the only real reason.