The civil war wasn't about slavery. Slavery was just the justification that Lincoln used to go to war with the South. Lincoln invoked abolitionism because the British had abolished slavery a decade prior.

The civil war was actually a battle over States Rights. The South was still an extremely rural place back in the 19th century, so most people were anti-government in some way, and on top of that the North was extremely industrialized. The two cultural differences became apparent by the 1850s when the government, which was heavily influenced by Northern politics, began to start implementing laws the South thought were unconstitutional. For about 10 years Southern states were seceding from the Union and ere gradually entering into a Articles of Confederation form of government, the Articles of Confederation were the original US constitution and were replaced within 10 years.

The North needed justification to go to war to save the Union, since the British were financing the South and the US government thought that the Brits were going to use the south as a staging point for reconquering the US (queue the US naval blockade of the South to prevent british imports into t South). Lincoln saw what the British had done 10 years prior and had helped absorb the abolitionists into the newly formed Republican party, the other members were Whigs party members and the Know-Nothing party members.

Once Lincoln got into office he used the heavy industrial might of the North to collide headlong into the South. The North also used border disputes, such as the West Virginia/Virginia secession crisis as justification to continue the war.

Towards the end of the war Lincoln regretted having to go to war in the first place, and that the main figure that enabled the civil war to happen was the weak willed Buchannon who was in a gay relationship with a democratic senator from the south.