Because the new protectionist tariff that would have killed the southern economy did not take effect until 1861.
Nonsense. First, if the south was so against tariffs, they could have easily blocked them in Congress if they had stayed. But the south was not even uniformely opposed to higher tariffs.
And I'll ask once again. Did England and/or France impose tariffs on American cotton? Did American tariffs, high or low, have any impact on the market price of cotton?
The "Southern" economy needed to die.
Walt