Step-by-step explanation:
Many Northern businessmen relied on the transportation of goods from the South to the North, especially in the trade of slaves as well as cotton, which was a major industry at that point in time due to the climate fit for agriculture. This cotton would be a necessity as raw materials for the Northern industries that would use them to make cotton products.
The south used slaves to great effect in the production of cotton. Opposing slavery would mean the reduction of the cotton supply as well as the decline of the slave trade that made their profits so high.