Although I feel people are more inclined nowadays to take a "cynical" look at this, and say that the abolishion of slavery was more a way for the North to project economic power over the South.

I say "cynical", but in this context it's actually perhaps an optimistic lens. Because if raw, selfish economics were what drove us to abolish slavery, perhaps we need not lament the abandonment of the moral hypocrisy of the times. Perhaps the hypocrosy wasn't really a driving factor in our social progress.

And that is, in fact, my view of the matter. As I've written elsewhere, "morality" as we normally use the term, is not a coherent concept. And instead, we can credit our success at cooperation as simply game-theoretical dynamics playing out among creatures that are all just vying for what they desire in life: https://medium.com/the-panopticon-publication/morality-is-personal-and-tribal-always-20c8c31f5d29