Reading the actual article instead of just the headline, here's a summary of their arguments. There are multiple powder keg situations around the world that are either exploding or simmering. Iran and its proxies, Russia and Ukraine, China and Taiwan. They could all turn into an interconnected war at any moment. Yet markets, which supposedly factor in these possibilities, are still very high.

What this is not saying is that another world war would be secondary to investor yields. They make that explicit:

This scenario would of course place financial damage a long way down the list of horrors.