Engineering it is simple once you have enough high-grade material. That was partly what that book was about. It was simple in the 70s, and it's totally trivia

Engineering it is simple once you have enough high-grade material. That was partly what that book was about. It was simple in the 70s, and it's totally trivial now, because the state of the art in ordinary manufacturing has made it so. No geniuses needed, or even engineering degrees, for the simplest designs. Yet it hasn't happened. It's not clear to me whether this is luck, heroic yet mostly secret effort by various national governments, something systemic to terrorism, or some combination. Well, we know at least that the CIA used to buy fissionables, no questions asked and no consequences meted, but I, at least, don't know how much they actually got that way.