The point here is that we don't need to build an iPhone, we only need a radio. Building a 8080 is much simpler, the USSR did it, the East Germany did it, China did it, all around the same time without too much difficulty. It's certainly would be much more difficult if the current civilization collapsed, but I think the author doesn't anticipate a total collapse, just a breakdown of the current economic system, thus it should be doable.
> Similarly the process for making a nuclear bomb can be written in a short paper, but few countries have successfully replicated it.
My understanding is that the physics of achieving the nuclear explosion itself is relatively straightforward. The real difficulties are to produce the weapon-grade materials needed, and to transform the explosion to an useful weapon, all under external sanctions, and even sabotage.
Taiwan had a nuclear weapon project in 1970s, significant progress was made in the beginning, if the U.S. didn't discover it and dismantle everything, it would be interesting to see how it turned out to be.
