How World War III became possible

Traditionally failing economies have gone to war to hide it from their people. People are much more likely to put up with hardship if at war is one reason. We see this in Germany in the 30s.  One reason for my concern.  Combine that with someone who seems to be fairly criminally inclined ...

The other side of it, if the worst happened, much of Europe, the US and Russia will be devastated and even there, there will be places not under the fallout that will remain completely habitable and not directly effected. Of course infrastructure will be quite disrupted and regional areas may become the new major cities. Conventional warfare may continue through that awful nightmare, though I can't imagine that enough infrastructure would be left to do much of that for very long, as armies are only as powerful as their supply train.

Simply the world won't be totally destroyed by all the nukes in the world, MUCH would be of course, just not all. Civilization will very much be changed. Imagine if you're in a small rural town in Tasmania. You might only lose a source of fuel, which of course is part of food production, though cuba got through it with very little fuel in the 'special times'. Everything will be in short supply and this will be true of countries not effected also, and there will be quite a few people still left. In terms of a long drawn out nuclear winter killing who is left due to starvation? ... I have my doubts based on historical records of events and the counter evidence is fairly good to the original claims made, though I'm not a climate scientist, and I'll go through it as I update my nuclear war story in another post.