@absamma It was the one-two punch of the bombings of Hiroshima and Nagasaki plus Soviet declaration of war. Important to remember is that the Japanese war council was deadlocked on whether to accept the terms of the Potsdam Declaration. Hirohito himself broke the deadlock to decide to accept the terms of surrender. Even then, that was followed by a failed coup to prevent the surrender.
Point is, Japan barely surrendered. I'm not convinced that if we change one aspect of how things went (don't drop the bombs, drop only one bomb, Soviets don't declare war) that a surrender happens. That leads to either further atomic bombs or a mainland invasion, both of which lead to the deaths of hundreds of thousands more. Soviet intervention could even lead to a division of Japan similar to how Germany was handled.
This sounds horrible to say, but the way things went may have been the best case scenario, at least if you only look at this as a metric of how many people have to die. You can object to the usage of atomic weapons in any capacity, which I don't think is necessarily a wrong opinion, but I don't think there was a clean way out of this.