True usually when something large enough happens people already know about it. Yet when I'm thinking about the fact that right now is just as dangerous as the Cold War, well, it really makes you stop and think. No one is really acting as though there is such a present threat, almost taking it all with a grain of salt. Yet, the Doomsday Clock really confirms it - There is a real danger here, our scientists and specialists say so, so please PLEASE actually pay attention and work to solve this.
Also, my understanding is that they don't just set it back when they realize things weren't as bad as they thought. It is more like, things were as bad as they thought, but people actually worked to set them straight and fix the problem. The clock went back in time a lot once treaties were signed between North America and Russia, once that nuclear threat wasn't there anymore.