I think that it is clear that the Civil War was not about slavery, for a large percentage of the Northern troops, as well as the Confederates.
The people in the North and South who were fighting over slavery were the elite. These groups were intermarried and they were the Democrats of those days.
In those days, the Democrats represented the interests of the Northern bankers and industrialists and the Southern plantation owners. The Republican Party in Lincoln’s day represented the factory and mill workers and farmers of the North and it was an abolitionist party.
The two parties switched voters over the next 100 years. LBJ’s Southern Democrats (Dixiecrats) were the last holdouts among Democrats to switch to the Republican Party, in 1968.
The wealth of the Southern plantation owners was tied up in their slaves, as an investment in capital. They ran the South, and they pushed for secession. They had resisted the abolitionist cause, through their States Rights movement, since 1835, in the Senate, starting with South Carolina.
Slavery in the North finally petered out in the 1830s.
If the Northern elite had not wanted to get rid of slavery, in order to get rid of the high capital cost of slaves, in order to take control of the Southern economy, then there never would have been a Civil War.
The carpetbaggers represented the investment interests of the northern bankers and industrialists in the South, after Sherman’s armies got rid of the high capital cost of slaves.
Slavery can be best understood as a labor issue when trying to parse out the reasons for the Civil War.
The role of the Carpetbaggers in securing Southern agriculture and industry for the Northern elite is key to understanding the war.
It should have been called the War of the Carpetbaggers.