Even though Truman became president by the death of Roosevelt I'm sure he was concerned about reelection. People would not be happy about losing men that they did not have to lose in a war.
Also I think racism played in the role of the bombings of Hiroshima and Nagasaki. Out of all the countries we were at war with the Japanese were the most different concerning their race. In America the Japanese were viewed as yellow belly savages. With most of the American public hating the Japs this made it much easier to decide whether to drop the bomb.
Another factor that can be debated is dropping the bomb because of our relationship with Russia. When Roosevelt was president we had a rather lose relationship with Russia. Roosevelt was good with keeping the peace with Russia, this was highlighted with his lend lease program during the war. Truman took a different approach. He had what analyst called the "hard lineaE policy. Truman did not wish to negotiate with the Russians. Truman was ready to play hardball with the Russians. No one can say what was the reason for the dropping of the atomic bomb. Speculation is that on