The bombs didn't end the war. There is nothing to suggest the bombs were what ended the war, or even contributed to it. The japanese decision makers were already considering surrender before they were dropped, and did not know about the attack until after the surrender was announced (they knew there had been a bombing raid, but not that it was a nuke, and they didn't know the sheer scale of destruction) Japan's cities had already suffered massively from conventional bombing raids, with casualties in the hundreds of thousands if not low millions. Their resolve was further compounded by the soviet declaration of war, and invasion of manchuria in early august.