> the goal of the bombing was to force an end to the war quickly instead of executing a protracted land invasion of the Japanese Home Islands - which probably would have killed more people (Japanese and American) than the bomb didWhile this was the rationale that was published after the war by the US government, current historical scholarship indicates that it was a lot more complicated than that. To give just a few key points:
Actual casualty estimates made by the US military in the spring and summer of 1945 for a land invasion of Japan were much smaller than figures quoted (without any specific sourcing given) in rationales published after the war. The latter figures were in the range of a half million to a million casualties, but the former figures were more like tens of thousands.
While it was certainly a goal of the Truman Administration to end the war quickly, if at all possible before the Soviet Union attacked Japan, dropping the atomic bombs was far from the only feasible option for doing that. In particular, there were plenty of indications (including intercepted Japanese diplomatic messages, since the US had broken the Japanese diplomatic code years before and was routinely reading all such traffic) that clarifying exactly what "unconditional surrender" meant, and in particular what the status of the Japanese Emperor would be, would have given the peace party within the Japanese government enough leverage to force a surrender sooner.
There is also plenty of evidence that at the very least Truman and his Secretary of State, James Byrnes, wanted to drop the atomic bombs in order to make the Soviet Union more tractable diplomatically and to reverse the much more conciliatory policy towards them that FDR had taken.
And finally, the internal deliberations of the Japanese government (which were not available to historians until some decades after the war) show that the impact of the Soviet Union invading Manchuria was much greater than the impact of the atomic bombs in pushing the issue for surrender. The Japanese weren't even sure at first what the atomic bombs were, and in any case the US had been firebombing Japanese cities for months so additional bombing was not a huge shock. The Soviets, however, had been stringing Japan along for more than a year at that point, holding out some hope that Japan might be able to get a negotiated peace brokered through the Soviet Union. In fact Stalin never had any such intention; he just wanted to make sure the Japanese didn't surrender until he had a chance to enter the war against them. But Japanese leaders didn't understand that until they were forced to realize it by the Soviet invasion of Manchuria (the same morning that the Nagasaki bomb was dropped).
Two good detailed references are The Decision to Use the Atomic Bomb by Gar Alperovitz and Racing the Enemy by Tsuyoshi Hasegawa.
> they also made several decisions that massively limited the amount of death - for instance, instead of picking relatively small military targets and staggering their delivery, they could've just dropped their three available bombs in one go on Tokyo, Osaka, and Nagoya and called it a day
The reason those cities were not targeted by atomic bombs had nothing to do with trying to limit deaths; they were not targeted because they had already been destroyed by firebombing in the months before the atomic bombs were ready, causing more deaths than the atomic bombs caused.