Looking back to now.
What could they have been thinking would happen when they behaved as they did? Surely any sane person, and most insane ones too, could see cause and effect well enough to know humanity could not survive permanently with vast numbers of thermonuclear bombs in the possession of large numbers of desperately contending people. The population had pressed the Earth’s resources beyond simple sustainability to where even water was a resource worth fighting over.
The problems were obvious to everyone.
Why didn’t they form a world government before the numerous Doomsday wars that almost obliterated humanity, and did exterminate most other species had been repeatedly waged. People fought until almost all of the bombs created, and hidden by that earlier age, some called The Atomic Age, had been found and exploded on some temporary enemies head. Later a much mutilated remnant population did revive a tiny semblance of previous civilizations, but only after the repeated Doomsday wars had proven all other alternatives impossible to live with permanently.
People were killing others because of what they might be thinking.
Whole nations had repeatedly fought over various mental constructs of how people should earn a livelihood, and the various legal systems which might be promulgated, and which of the various families which might rule over the public. But, those things were finally realized to be nonsense. It had come down to a very few problems that needed to be solved or else humanity would die an early death. Once these problems were addressed and stabilized the people of Earth could live long and peaceful lives.
Humanity can not tolerate Weapons of Extermination.
Perhaps one of the easiest problems to solve, after numerous Doomsday wars, was the convincing everyone that the Weapons of Extermination (WOEs) must be controlled by a single entity, who themselves must be carefully controlled by unknown others, and a tightly controlled system of judges, who themselves had no access to either weapons or to political power. Also, there was a legal control of certain types of information related to these and all other types of WOEs, which seem harsh to the ancients but which were found to be essential and therefore were tolerated by the later people. Only the very limited number of people had the legal access to information about WOEs, and they had absolutely no access to the materials necessary for making these weapons. They were permitted to have knowledge of how to make them so they could know how to prevent others from making them. The physical apparatus was broken into numerous sub-components which are made by people with no knowledge that they are also components of WOEs.
The knowledge of how to make WOEs must be absolutely hidden.
The hard part for the ancients to accept was that individuals who were searching for information about WOEs or how to make them were quietly eliminated. They simply died without any apparent reason. They had a heart attack or some other normal event which lead to their ceasing to exist. It sounded harsh to the ancients, but there were very few people who were seeking these devices, and so the absolute number of these unusual fatalities was thought to be very small. This loss of a few overly curious people was balanced by the survival of untold billions of other normal people. Once all humanity accepted this restriction and lived with it, and accepted the very light constraints of not seeking WOEs, the Doomsday wars ceased. Once the laws were in place it was all done so quietly it was invisible.
We face Doomsday every day but people of the future will wonder why.