Industry, the north was an industrial monster. You could have all the money you want but if you don’t have any factories to build weapons you’re fucked. The largest Iron mill for the South was located in New Orleans and New Orleans was taken over Fairly quickly by David Farragut. That’s why you see very little confederate iron clads. The south just could not produce enough war material. Even bullets would sometimes have to be crafted by individual soldiers since the musket was forged and not produced in a factory making it shoot a specific round that wasn’t masses produced.

That being said we also forget that for a while the confederacy had a very good chance mainly due to military leadership. But brilliance doesn’t make up for lack of guns