Easier than you might think in early Republican Germany - despite the fact that it's been rightly praised as the most progressive country in Europe (early strides in gay and transgender rights, early strides in women's rights, they had women under arms fighting the USSR, the country was a haven for black musicians from the US...), in the early days the extreme right were everywhere, anti-Semitism was a major problem...combine that with the economic problems they had in the early days, you could see even a more lunatic fringe candidate getting power if he used the right words for the masses. But it'd be pushing ASB to have Hitler get to be in Germany at the time...
It's very good it didn't happen of course. IRL, Germany's a progressive country and has basically been the dominant economic and military power on the European continent since fighting the Sovs. Some lunatic fringe type taking over could have caused all that to be undone...