It wasn't fought for that reason. It was fought to reestablish Washington DC control over the money stream created by Southern exports to Europe.
Had the South been able to maintain it's independence, most of the European trade would have shifted form New York to Norfolk, Charleston, Mobile and New Orleans. The North was fighting over a pile of money that flowed through the hands of the "elite" in New York and Washington DC.
I stumbled across this map years ago which purports to prove the war couldn't have been about tariffs, because the vast majority of tariffs were paid by New York city.
At first glance, this looks compelling, but when you learn that 74-83% of all export value was produced by the South, you realize those import goods were payments for those southern exports.
Somehow the system had been rigged to send product out of Southern ports, and bring profit in through New York and Boston. I didn't learn how it had been rigged until later.
Washington went to war because 80% of the European trade represented by that pile of coins on New York and Boston were going to be taken away from them by an Independent South. This is why Lincoln was willing to offer them the Corwin Amendment in an early effort to talk them out of leaving.
The war was not about slavery, it was about money. Specifically the money that went through the hands of Lincoln's New York wealthy backers.
This is "Deep State"/"Establishment" stuff, and this is exactly where it began.