Did the American civil war suppress corruption? If so what corruption did it suppress? My read is that is basically started us towards the corrupting influence of overarching federal control. But I may be looking at it myopically.
The short answer to your question of “what corruption did the Civil War suppress?”
Slavery. Slavery was an institution that was coming to the end of its practicality, but was sustained in place by a series of compromises made between the bankers of the Northern states and the slaveholders of the Southern states, where slavery was held to be still legal. The cause of the Civil war had little to do with freeing the slaves (that was a bonus announced when the war got under way), but a great deal to do with a falling out between the bankers and the large plantation owners, who had come to rely far too much on slave labor, while the bankers saw their investments in the cotton production industry going away. Punishment had to be exacted. The corrupt bankers and the corrupt slave owners were both punished by impoverishment.