One State`s reason does not negate the underlying cause.
What they didn`t completely understand was basic economics.
Slavery was economically untenable. The fact that either those in the south or north didn`t get it is testament to their undeveloped economic theories and practices.
“servile labor disappeared because it could not stand the competition of free labor; its unprofitability sealed its doom in the market economy.” (mises.org/pdf/humanaction/pdf/ha_21.pdf)
Which was?