In retrospect, it wasn't even necessary, given the sad state of the Japanese wartime economy -- the US wasn't very far from overwhelming them with conventional warfare. But such things are more obvious to leaders in retrospect, especially when they haven't been in a war mindset for years, fighting a string of incredibly nasty battles one island at a time before coming to the islands named 'Japan'....

But either way -- you can say it was the right decision or the wrong decision -- it was hardly "for no reason".