Nice misdirection. The northern manufacturers & industrialists didn’t support the war. They were just as happy to sell to the southern slaveholders as a separate country as they were selling to them as fellow countrymen.
Of course, there was a little more of a ruckus raised over the Nebraska Territory & Bleeding Kansas, over the California & New Mexico territories, over John Brown & Gabriel & Nat Turner, over the House’s gag rule prohibiting debate on any anti-slavery issue, over over the Tanney court & their Dred Scott silliness, etc etc etc. It’s funny how even though the war wasn’t about slavery, every controversy that led to the war was always fundamentally about the two very basic question “should it be legal to own slaves?” and “should we change existing laws to make it illegal?”
BTW: You’re wrong about the Northern industrialists. Where do you think Abolitionists got most of their money?
The Northern industrialists couldn’t compete with European goods. Part of the issue was that European manufacturing was better established than American - their goods were cheaper even after being shipped across the Atlantic; part of it was that currencies were not as fungible as they are today. Merchants couldn’t bring home pounds or francs and trade them like today; they certainly couldn’t bring home specie ir bullion - the host nation wouldn’t allow it! And ship owners certainly didn’t want their ships to return with empty holds.
In the meantime, most of the Federal Revenue came from the South (and was spent in the North!). With the South gone, Federal income would drop dramatically. However, that wasn’t all! The Confederacy planned a 10% tariff (very low) in their ports AND controlled the mouth of Mississippi. The Northerners foresaw a bankrupt Federal Government and grass growing the streets of New York and Boston.
That, more than anything was the reason for the Civil War.
Or else why did Lincoln himself say that he would have a Union with or without slavery?