The economics of slavery were quite healthy in 1860. The wealthiest people in the country in 1860 were Southern plantation owners. Cotton was King and it was far more profitable and far less risky than steel, coal or railroads --- especially when you had slave labor. The industrial revolution had hardly touched the south and did not for another 40 years after the war was over and the slaves were free.
Well duhhhh... After the war the congress again passed huge tariffs which only raped the souths economy. I mean, it doesn't take a rocket scientist to figure this stuff out.