Nope, it was about who would control the money that the slaves produced. Slavery was making the Union a lot of money, and so long as that continued, there was no problem.
The problem arose when the South wanted to stop so much of that money from going to the North.
The North wasn't going to tolerate that, and so they launched a war against the South to stop them from stealing the European trade away from their control.
So the war was about money and power. "Slaves" were only incidental to the larger struggle taking place.
Where in your Confederate Apologetics Economics textbook did you learn to separate slavery from the value that slavery produced?