Pay attention to the similarities between right now and the early 1930's when the Depression really began to take hold.
Countries fight over the dwindling share of consumption in the world by trying to export their way out of their essential problem which is demand ... dropping beyond the means of any remedy. It's a zero sum game that eventually flatlines, leaving a glut of goods, no buyers and a pile of fiat currency which is effectively worthless.
World War II was started for the same reason that World War III will be. As a last minute act of desperation to try to stimulate demand.
Same old humans. Bigger weapons by far this time around. The last world war was counted in millions of civilian casualties, the next will be measured in billions.