The war was not fought over ending slavery but was fought because the North did not want to let the South decide it’s own destiny. Tariff income on most of the imported goods used by the South was a huge money maker for the North and the North didn’t want to give it up. The issue of slavery being allowed in new territories was used to politically weaken the South to the point of being dictated to by the North. The South had had enough and wanted to determine their own destiny. The North FORCED their will upon the South, then used “slavery” as an excuse for the deaths of over half a million young men. This was not a noble effort.
It was more than just tariff revenue, it was 75% of all European trade with the United States. 75% of the money earned by exports were produced by Southern products, and New York was cutting themselves into 40% of every dollar in sales. This map below illustrates how they had jiggered the money stream to come back through New York.
The Southern trade employed New England Shipping, Banking, Warehousing, and paid for a lot of material from Northern Manufacturers.
Not only would Southern Independence divert that money stream out of New York, the additional 40% in revenue gains would have funded Southern competition for existing Northern Industry. (The people who backed Lincoln owned that Northern Industry.)
No, there was far more at stake than merely tariff revenue. The cost to the North of allowing Southern independence was massively greater than 65 million per year in Tariffs. The South was a serious economic threat to the existing monied power structure in the North, and *THAT* is why they could never allow it to be independent of their control. *THAT* is why the first thing Lincoln did was to throw up an economic blockade.