Answer:
It is quite controversial but I think he was in the right.
Explanation:
Let's say he didn't drop the atomic bomb. Instead of 225,000 Japanese dying, it would be 100,000 Americans and 200,000 Japanese because of the battles on the Japanese mainland. This is an estimate of course, it could be less, but the fighting would be drawn out and the troops would die of diseases and he wanted to end the war as soon as possible.
"There is no instance of a nation benefitting from prolonged warfare." - Sun Tzu, The Art of War