A war of numbers. The North was both more popilated and industrialized, and therefore had control of most of the weapons and ordinance production. The South being less populated and industrialized was thought to be easier to gain control of, and there had been a gold rush not
long before the Civil War, which would interest powerful
people in North to regain control of a seceded part of the union. Since the North wrote the history books, their version of
history was always going to be the more popular and noble sounding version of history, but not everything in a book is to be taken without a grain of salt, any more than any other source. Most wars are
money/resource/power struggles once you get below the surface, with headlines about abolition and emancipation from slavery being icing on the
cake that gives
people a warm, boosted ego, even if the
people that started the war had no true interest in or gave a fuck about a single black/ African descendant since it's rare that ones that started the war are the same ones fighting in it (Washington being an exception).
The history
books tell
people the Civil War was about freeing the slaves to make
people feel good inside because it sounds good, but for the average person fighting in it on either side, slavery was the last thing on their mind.