He saved a lot of American lives. That’s all that matters.
But it bears stating that he saved even more Japanese and Chinese lives. Magnitudes more. And all the POWs/Internees of various nationalities held by Japan throughout Asia who were to be executed when an invasion occurred.
Why Truman Dropped the Bomb from the Weekly Standard in 2005 is a must-read on the whole "Japan was ready to surrender" lie.
He saved a lot of American lives. That’s all that matters.
In case that is not all that matters, recall that the Japanese (through starvation, disease, battle casualties, and brutality) were causing about 250,000 casualties A MONTH, mostly Chinese civilians.
And the brutality was so bad that the author of “The Rape of Nanking” committed suicide because she could not remove those images from her mind.