The North was prospering more.
Who was servicing those goods produced at least in large part by slave labor? The banking, shipping, insurance, “factors” (ie warehousing and logistics). Where was the tax revenue collected on the goods exchanged for those cash crops being spent overwhelmingly? Oh that’s right, in the North.
In addition to this article posted by the Abbeville Institute could have been added a whole slew of editorials in the leading Northern newspapers - which I’ve posted here before. They were abundantly clear that to them, it was all about money.