Question

What led to the rise of fascism and aggression after World War I, and

Answer 1

The rise of facism was caused by the Allies presenting Versailles to the German Empire later becoming Weimar Republic. The Weimar had to demobilize their armies and they had to pay large debt. France occupied the Rhineland because it was industrial heart of the Weimar. This lead to people start supporting facism (Nazis) and the communists. The other nations like Italy got inspired by this and they became facist have a good day

Answer 2

Answer: from 1900 one can observe steady growing questioning of liberalism, liberal values and all the Enlightenment trends with European civilization (liberal and democratic paradigm was introduced by Enlightenment and French revolution). This questioning was stimulated by 1) social Darwinism and consequently by biologization of social sciences, 2) anti-semitism (present everywhere in Europe), 3) there was a profound need of some religious need (reaction against secular Enlightenment values and mechanicist and materialist paradigm typical for Enlightenment, Marxism, communism) .....this need was partly satisfied by the discovery of the unconscious ....fascists became great partisans of "bodily revolution" (Drieu La Rochelle), believed that the "body instinct" is more true than "cerebral intellect" ...all that was part of  a revolt against reason, cult of irrationalism 4) there was demand (in results from 3) for a strong leader, 5) Italian sociology of elites (Lombroso, Michels and others). Aggression was viewed as vital, life was viewed as something that should be based on instinct and vitality and not rational speculation.

Explanation: fascism and question of power (and its unconscious roots) was strongly present in European culture during the first part of the 20th century.