Hitler wasn’t brainwashed specifically, but the social & economic conditions in Germany post WW1 pretty much ensured that some form of a “Hitler” was going to come to power there regardless. Germany lost a portion of their land which was significant to their economic production in the Treaty of Versailles as well as having to pay the equivalent today of 33 Billion in reparations. This combined with the effects of the Great Depression a decade later caused Germany’s economy to tank and many people blamed their loss in the War on the left-wing and Jewish leaders. It was similar to the current social climate of the US today except much more inflated. This gave rise to several right wing, conservative parties and Hitler took advantage of the moment. He was definitely a particular evil, but he was also a product of the socioeconomic & political environment post WW1