In his time, Hitler was ridiculed for his weird looks and barely coherent speeches. It was thought he would be ineffectual and easily controlled by more seasoned politicians when he was allowed to become cancellor (he only got about 35 percent of the popular vote but managed to build a conservative coalition). To underestimate his and his party’s plan to dismantle democracy, which was plainly laid out in Mein Kampf, was a grave mistake of course. More info here: https://www.annefrank.org/en/anne-frank/go-in-depth/germany-1933-democracy-dictatorship/