>>508038579 (OP)During WW1 both Russia and Germany were trying to court the jewish population of Poland and Slovakia to persuade them to rise up against the other and join them. This consequently fomented conspiracies by both sides that setbacks on the battlefront were caused by jewish spies and defectors aiding the enemy.
When the russian revolution happened, the white russians put forth a conspiracy theory that vengeful, anti-monarchist jews had invented communism, returned from exile to subvert the populace and started the revolution purely to get revenge on the Tsar for oppressing them. The conspiracy theory went as far as claiming that Lenin, Trotsky and Stalin were all secretly jewish germans.
During the paranoia of the red scare, the conspiracy theory became popular, especially because both the Entente and the german empire took turns backing the whites against the reds and had a vested interest in pushing the white russian's narrative.
When Germany lost WW1, the leaders responsible for the defeat, Ludendorf and Hindenburg, formulated a conspiracy theory to save face that revolved around an anti-monarchist conspiracy stabbing the military in the back and staging a bolshevik revolution to depose the Kaiser. As labour movements in Wiemar Germany rose and the red scare proceeded, the two conspiracy theories merged and the Germany right wing became convinced that a "judeo-bolshevik" conspiracy had cost them the war and was now invading their country to destroy their race.
Hitler evidently didn't just capitalize on this narrative but wholeheartedly believed it and made it a central fixture of his domestic policy.