Which event contributed to the growth of communism and a worldwide depression after 1918

I would say that this would be the WWI that contributed to the growth of communism and a worldwide depression after it as it became very clear after that WWI was not about 'fighting for king and country' but simply about the imperialist division or re-division of the world and just saddled the workers of the countries who participated in the war with excessive debt and that is when the first socialist country was declared in 1917 in the Soviet Union.