I think we will never know what the reasoning behind the two bombs really was. I could imagine that after using large scale carpet and fire bombing against civilian targets, a nuclear bomb with a similar effect doesn't make much of a difference.
> They were more afraid of the red army than 2 nuclear bombings...
Not according to them[1]:
"More than ever before, the historical record confirms what those soldiers knew in their gut: Hiroshima and Nagasaki, hideous as they were, shortened the war that Japan had begun and saved an immensity of lives. Far from considering itself essentially defeated, the Japanese military was preparing for an Allied assault with a massive buildup in the south. It was only the shock of the atomic blasts that enabled Japanese leaders who wanted to stop the fighting to successfully press for a surrender.
"'We of the peace party were assisted by the atomic bomb in our endeavor to end the war,' Kido Koichi, one of Emperor Hirohito's closest aides, later recalled. Hisatsune Sakomizu, the chief Cabinet secretary, called the bomb 'a golden opportunity given by heaven for Japan to end the war.'"
