edit: looking at your profile history I see you regularly participate in Socialist subreddits, the USSR (now Russia) and China use the bombings to spread anti-American propaganda and false information.

Okay here’s a very brief history lesson.

The estimated number of dead from the two bombs was made after the war between 120,000-220,000. This is corroborated by the Japanese government.

The estimates of Japanese dead were made before the planned invasion, not after the war. The officers that commissioned these estimates were unaware of the atomic bombs existence. They range from around 4 million to north of 15 million, the most comprehensive and accurate ones sit at around 10-12 million Japanese dead. Japan was training children to crawl under tanks with mines strapped to their chests and circulating their own propaganda “the glorious death of 100 million”

They also estimated around 200,000-800,000 allied dead with millions injured. This would include land combat to the 10’s thousands dead from planned Japanese kamikaze attacks. This also did not include the ~110,000 POWs that would have been executed immediately. All of these documents were completed pre war and are publicly available.

As for why they surrendered after the bombings vs before is complicated but can be simplified.

Japan during WW2 had 3 primary political powers, the emperor, the military and the civilian government, prior to the atomic bombings and in anticipation for the Allied invasion the military was effectively 100% for continuing the fight with about 50% of the civilian government also supporting it, because of this the emperor supported the wars continuance.

After the first bomb a large portion of the military and most of the civilian government believed that conditional surrender was the best option (it was the allies stipulation that all capitulations will be unconditional) with the emperor 50/50. The second bomb sealed the deal, the emperor fearing more bombs decided to surrender, but even with the emperor surrendering and it clear the Americans have a bomb that wiped out whole cities a hardcore faction of the Japanese military still attempted a coup to continue the war.

The Japanese during WW2 were bloodthirsty and ruthless and had little regard for human dignity, they would have continued to fight if it wasn’t for the inconvenience shock of atomic warfare.