I instantly realized this image was proof that New England was somehow monopolizing the European trade, and basically intercepting much of the money produced by exports from the Southern States which produced around 3/4ths of the value of all exports.
Lincoln launched that war because it served the interests of the New England Robber Barons who held his strings.
Great graphic sez it all.
Strong evidence suggest as just as you suggest -- the war against southern independence was launched as a war of economics. The South was the source of much of the natural resources funneled to northern factories and ports (NYC, Philly and Boston.)
Were the South to expand on its own trade and improve on its own ports and financed and built its own factories, the monopoly of those "New England Robber Barons", its Northern ports and factories would obviously have been jeopardized. As would all that tax revenue generated from the South. Europe could sail directly into Charleston or New Orleans, bypassing NYC and Boston.
We'd noticed just after the CW those same Northern "Robber Baron" elites and carpet-baggers were given carte blanche by Lincoln's successors to sweep through a South like locusts and vultures, buying out a devastated people of its lifeblood -- its business, property, and assets for pennies on the dollar. That feral gummint helped the elites steal wealth -- just like today.
They then used that newly acquired wealth with which to help them run roughshod over Indian territory to expand railroads and build towns without due compensation OR despite treaties. Funny how history repeat itself, isn't it?
So yes -- it can definitely be said that the Elite-class controlled and owned politicians and created the Civil War to enrich THEMSELVES. "Sovereignty"? "Slavery"? Keeping the Union together? Not so much.
Something else I remember today was the massive surge in corruption which occurred in the aftermath of the civil war, especially in the New England and Washington D.C. areas.
The Grant Administration was especially known for it's corruption, influence, kickbacks and financial scandals, though Grant was generally seen as a dupe, and not a participant.
The question occurred to me, just where did all these New Englanders get the idea that corruption and influence peddling was okay? Well they got that idea from the huge success they had in creating the Civil War!
By making the US go to war for their economic interests, they had laid the foundation for all that future corruption. It had become the way of doing business between New York and Washington.