I'm not a big fan of estimates on the atom bomb deaths. The 1946 estimates by the Manhattan Project were 78K Hiroshima and 35K Nagasaki. Perhaps underplayed so that the U.S. doesn't look evil. Estimates since the 1970s (after it became fashionable to say the U.S. is all things evil) are 140K Hiroshima and 70K Nagasaki.
I don't like either estimates because I don't like people playing with numbers to send a message, in either direction.
This I know for sure from poxy measurements:
1) Total Japanese deaths from the island hopping: not enough for Japan to surrender.
2) Total deaths from firebombing mainland Japan (plus prior deaths): not enough for Japan to surrender.
3) Total deaths from 1st atom bomb (plus prior deaths): not enough for Japan to surrender.
4) Total deaths from 2nd atom bomb: enough for Japan to surrender, and that's what mattered most.
that’s not the point- a lot more people would’ve died if the US & allies attacked the Jap mainland, in the effort to get them to surrender, then died after the bombs were dropped, which ultimately led to their surrender...
Well, to be truthful, even after the 2d A-bomb drop, most of the Japanese High Command was hesitant to surrender, and there was even a coup planned by mid-senior officers to take over from the High Command, gain control over the Emperor, and refuse to surrender. In the end, it took a direct Imperial Command from the Emperor to order the surrender.