The Japanese were prepared to fight to the last man, woman, or child to defend the home islands. They were geared for war in a way that is hard to understand from a modern perspective. They were propagandized heavily.

The other thing to recognize was that the USSR had declared war on Japan the day before Fat Man was dropped on Nagasaki. This violated the Soviet-Japanese non-aggression pact. Before this there was hope that the Soviets could advocate for better terms for Japanese surrender. The Japanese Supreme Council was firmly opposed to ending the war. After Nagasaki, Hirohito intervened in the council and ended the war.