Answer:
those bombs where the first ever in history where nuculer weapons were used in combat.the bomb was not in fact a necssity but was maibly used for an experiment since it was the first time ever being used.it started due to the kamikaze attack where japan was not surrendering,japan had caused a huge impact and loss for the us getting japan heavily targeted for there manhattan project for an nuclear bomb.
the US had many options from getting japan to surrender and didnt have to drop two bombs in two different cities,the event was more of a experiment of accuracy for there invention instead of revenge.you can clearly know that if the US didnt have an option and was deeply required to they wouldnt use two bombs since it was valuable but since it was getting tested they had no problem of using two.