Bad people sometimes do things that lead to good results and vice versa.
A political solution may have been possible had John Brown not inflamed passions. Eventually slavery was going to end and the South’s economy would have to adapt. However, many in the South felt that they were under unjustified attack and decided to fight back. IMO, right principle, wrong application/set of circumstances.
That's actually a myth since the 1860 Census showed that planters were actually transitioning their slaves over from the cotton and tobacco fields to the nascent industries, especially mining, that were beginning to take root in the South, about twenty or thirty years behind the North.