The struggle between dictatorship and democracy was long due because of the suffering of the European nations in which autocracies were in power ever since the formation of these countries i.e. Russian Federation, Germany, Italy etc.
Ideologically the Russian Revolution, National Socialism of Germany, Fascism that emerged in Italy were movement towards that were same and its ultimate goal was the same i.e. establishing a socialist society.
The reason of Russian revolution was again in favor of socialism, but it was a hard form of Socialism that was called as Communism. It also threw away the Tsarist monarchy and socialist country.
De-colonization at the time looked a move towards democracy but in the larger sense it was a pretext for puppet democracies that were supporting the great powers at one point or another depending on their interests.
The Versailles treaty was the cause of National Socialism and the movement did not challenge the leftist ideology of the Western Status quo but it was National Socialism that challenged far-right of Western society. Italy in the aftermath of WWI sided with the Axis powers because of ideology of Benito Mussolini. (Daniel 2010). The same was the case with Fascist Italy.