The world became a more dangerous world when scientists learned how to weaponize atomic energy. Most of the great powers in the world had interest in such, but it was the US that achieved it first. The story of the development of nuclear weapons was one that came from the perceived weapons race that came about due to the Second World War. Had the Axis powers acquired the nuclear bombs first the resultant catastrophe perceived would have perhaps allowed them to win the war. Knowing now the results of the Holocaust, the war crimes of Unit 731 of Japan, the world then feared the worst if the Axis were to have such a powerful weapon. Fortunately for humanity there was some (a subjective term, yes) restraint in use of the atomic weaponry, beginning with a one city by one city toll, waiting for the Japanese response to each bomb.
Nuclear power changed how people perceived the future. Some assumed the future would be progressive, star reaching, futuristic, magnificent and positive. Others assumed that once the rest of the world achieved nuclear weapon development, the world would become a stateless anarchic world, filled with warlords, and power hungry evil leaders. The same kind of dualistic views filled the minds, of fears and hopes, of fiction writers and artists.
Heroes of an icon nature, from companies like DC comics, the hero might gain powers from an event, and thereafter be changed and able to wield the atomic powered power. The change was often seen as, the character being a living nuclear bomb. Each had God-like powers, and the use of power was then both a question of heroics, and ethics.
Characters from Marvel, on the other hand were changed, given powers, but the radiation mutated the persons and they became changed and evolved, or so, as a result. Marvel had other heroes who were born different, called Mutants. They were seen as being a new species of human.
The INCREDIBLE HULK
The FANTASTIC FOUR
THE X-MEN, born different, gathered to fight evil MUTANTS