Yes, it was, but not for Japan. If they had given Japan more than three days between Hiroshima and Nagasaki to think it over they’d have likely surrendered, but defeating Japan wasn’t really the point. It was a show of force for the rest of the world (especially the USSR) to say "we are the new rulers of the world, bow down and submit or we’ll glass you too".
Yes, it was, but not for Japan. If they had given Japan more than three days between Hiroshima and Nagasaki to think it over they’d have likely surrendered, but defeating Japan wasn’t really the point. It was a show of force for the rest of the world (especially the USSR) to say "we are the new rulers of the world, bow down and submit or we’ll glass you too".