But these things are the province of speculation, not knowledge.
Think for a minute about what this essay is asking "What if action X did not end the war in the Pacific?"
Well dang, Action X could be just about anything. The fact of the matter is that all of the actions, taken together, were the reason for the war to end. Yes, Stalin played a big role. But it's not an either-or situation; it's an amalgam. The logical structure of trying to support a statement such as "The Bomb Didn't Beat Japan" is flawed. It's like saying the landing on Tarawa didn't beat Japan. Well no, and yes. The assertion itself is flawed.
While I love all sorts of semi-non-fictional essays, I have a little warning bell that goes off when I'm mostly through an essay and the essayist starts telling me a story about how I've been misled. Smells of a political agenda and manipulation.
Japan was threatened on many fronts and made the best choice it could. That much is clear. Atom bombs did not cause as much building and population damage as the fire-bombing did. That's also clear. But atom bombs represented one thing that Stalin and fire-bombing did not: the end of Japanese culture. A few dozen atom bombs would not only have made huge holes in the landscape, it would have erased the culture of Japan.
Nobody is finding comfort in simplistic stories. In fact, the more details people know, the happier I am. But dropping the bombs on Japan saved millions of both Japanese and allied lives. It served as a quick end to a long war, and it saved thousands of allied prisoners whom the Japanese were ready to execute. It also allowed the great Japanese culture to continue.
Most serious historians don't get into counter-factuals, except maybe as fiction. It just doesn't work.