While the genocide in Africa might have been normal machinery of empire shit, giving heavy weapons to a bunch of psycopaths saying they want to do a coup, them doing a coup 4 years later, sending entire political parties to concentration camps were not normal at all.

Dude was only mad that the nazi party violently consolidated around a group that didn't like him.

The social democrats were terrified of the workers turning to communism and destroying the Wiemar Republic to build a Leninist dictatorship of the people—a government steeped in authoritarianism and secret police. So they put their weight behind the Nazis in street-battles between brown-shirts and white-shirts. They failed to recognize that by lending legitimacy to any worker movement advocating for authoritarianism and secret police they were signing their death warrant. The Nazis were never that popular but the social democrats authorized the people to tolerate them, even if they didn't like them. The result? Hitler manipulated everyone around him into giving his party more and more power in the name of avoiding Communism. The very first thing he did after becoming the totalitarian authoritarian dictator? Make a pact with Stalin. Again. The Social Democrats created the perfect environment by co-signing Hitler to allow the very thing they were scaredest of to happen. That's why today you see anarcho-communists telling their followers to do things like "don't get involved with Wagner's uprising against Putin. They're not your friends. They're just a slightly different kind of fascist. Best thing we can do is sit back and them bleed eachother."

So that's... One full exploration of how the social democrats enabled Hitler, but there's also another. What did this band of pacifists do as Hitler plunged the world into the most deadly conflict in human history? Did they organize uprisings against him? No. They just kinda planned to wait him out, and remove him through peaceful means. That ship had sailed already but they didn't really get on board with the resistance movements going on within Germany either. If they were in modern times they'd be the people telling people not to march with the Black Lives Matter protests because the best way to get reform is via petition and working within the system. Bear in mind that Hitler completely threw the system in the trash and that the new system in his regime didn't really give room for anyone to resist him through legal means. The social democrats were the leaders that most Germans liked and respected. They were still community leaders, and I think they failed to recognize that a lot of people looked to them for guidance on what to do about Hitler and what they saw was to just go along with it, tolerate all the violence, and hope a better day would come.

If you're interested in an actual good journalist instead of some internet rando talking about all this check out Behind the Bastards: How Nice, Normal People Made The Holocaust Possible.

The Quuuuuill made a great general response, but a couple important specifics:

1. While he did touch on it, at the end of WWI, Germany had a revolution, the November Revolution. During the latter part in 1919 the Social Democratic Party, SPD, won the election, and their candidate, Friedrich Ebert, became president. His administration proceeded to arm paramilitaries such as the Freikorps to brutally stop the revolution. This included mass executions and targeted executions of communists such as Rosa Luxembourg.

This ultimately resulted in the liberal, anti-communist character of Weimar Germany which created the conditions for fascism.

2. In the lead up to the elections of 1933, NSDAP ran Hitler. The communist part, KPD, and SPD talked about the necessity to beat hitler, and agreed to run 1 candidate to avoid splitting the vote. The SPD then proceeded to renominate the current president Hindenburg, an extremely conservative aristocrat and promoted unity and stability in all of their campaigning.

The KPD, ever cursed with Casandra Syndrome, ran their own candidate and campaigned on "A vote for Hindenburg is a vote for Hitler, a vote for Hitler is a vote for war"

And then Hindenburg won, with just over 50% of the vote. And then in the name of unity and stability, proceeded to make Hitler Chancellor and put nazis into other positions of power, setting them up to trivially coup the government.