There is a lot of energy in nuclear bombs, that doesn't mean they are a sustainable basis for human society... We consume and waste more than energy. Currently, Toilet Based Societies consume the resources of 1.7 planets per year.
The limiting factor is energy. There's plenty of space for the current population, and even for a much larger one if we wanted, and modern agriculture is very efficient. You just need a lot of energy to move people and stuff around and power all the machinery. And that can't come from fossil fuels.
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You may also notice that the sun isn't actually on this planet, so there's that.
Also, why did you bring up nuclear weapons? Do you have some sort of hangup about nuclear power?
The point is we don't just need energy. We need nutritious food, We need clean water. We need healthy spaces for living.