Abraham L.
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Preserving the Union (ie the all-powerful central federal government that we all know and "love" today) was the overriding goal.
Incidentally, the internal revenue code all by itself (not to even mention all the other outrageous laws on the Union books) should be a cause for violent revolution among a truly freedom loving people.
More like preserving the money flow into Northern pockets. The South was producing 72% of the total trade with Europe and that meant 72% of the revenues raised to fund Washington DC came from the Southern states.
The threat to the Northeastern elite's pockets was more than just the loss of that trade revenue from Southern trade with Europe. Without the protectionist tariffs, the Southern states would be importing massive quantities of European manufactured goods, and they would be reselling those products all along the Mississippi river watershed and all along the porous border with the Northern states.
The Wealthy powerful elites of that era (who controlled Washington DC just as they control it today) would have been devastated by the loss of their captive markets and they would have been financially ruined.
Additionally, other states would join the Confederacy due to it's economic prosperity and this would further erode the power of the Liberal elites in the Northeast.
The war was about massive amounts of money which would have been lost to the "robber baron" class in the Northeast.