As you can see in my reply (which is veering dangerously close to the size limit on HN, which is why I'm replying to it instead of adding this to it directly), responding to a false claim and debunking it takes a lot more writing and effort than simply stating it and moving on to the next one.

The NSDAP was far right. The vast majority of political and historical scholars agree on this. It was also decidedly not socialist. By the 1930s it also was no longer anti-capitalist in any meaningful way (again: working class populism isn't socialism, otherwise Tucker Carlson would be a socialist).

By focusing solely on the USSR and the NSDAP you're also ignoring countries like Mussolini's Italy or Franco's Spain and the Second Portuguese Republic. These states were as much alike as they were different but if you pay enough attention you might find a better pattern than "socialism is when authoritarianism".

The USSR was authoritarian. When the Bolsheviks came to power, they disbanded the workers councils (which btw is what "soviet" means, ironically) and trade unions because the Bolsheviks thought that Russia was too agricultural to be capable of having a true communist revolution and needed the party intelligentsia to figure out how to apply communism for the people. Lenin actually disagreed with Marx on many things, which is why the school of thought based on his writing is known as Marxism-Leninism, not simply Marxism. Specifically Lenin's followers generally think that Marx only described the end goal and Lenin described how to get there. Demonstrably, he did not get there, however. It's worth pointing out that even the USSR and its like agreed on this, which is why they referred to their states as "real existing socialism" (to contrast their systems with "utopian socialism", i.e. what they initially stated would be the end goal but eventually argued was impossible to achieve).

I understand that the American right and its many copycat right-wing movements across the Global North often think "actually the NSDAP was the national SOCIALIST party and it was left-wing" is a nice and easy way to smear anyone left of Reagan but what I want you to understand is that this is not only untrue but also severely misunderstands the extent of the suffering the Nazis inflicted and wanted to inflict. "What if the Nazis had won" makes for entertaining television but in reality it would have meant the systematic death of thousands of millions of people.

The Nazis did not win an election. They did not overthrow the government. They were lifted into power by the Christliche Mitte, a center-right Christian conservative party, because the right saw them as the best weapon against the rise of socialism and the (at that point) imagined threat of a communist revolution[0]. When leftists today talk about "enabling Nazis", this is what they're concerned about. All of Germany did not need to be Nazis for Germany to become Nazi Germany. It didn't even take a majority of voters, let alone a majority of the population[2]. It only took a large enough group and an even larger group of right-wing "moderates" that felt comfortable enough with them to hand them the wheel.

The USSR on the other hand was the result of a revolution. Unlike what the USSR said, this wasn't a revolution of the Bolsheviks although the Bolsheviks had the same enemy: the czar. But the Bolsheviks were the strongest and best organize left when the dust settled and they took the opportunity, first by integrating leftist movements, then by abolishing them, eventually by destroying them. Instead of giving power to the people they said they themselves were the people and they gave all the power to themselves. Instead of ruling bottom-up by delegation they built a bureaucracy and an intricate tapestry of elections and representation.

If you want to understand socialism, you're better off reading Bakunin than Lenin, Bookchin than Stalin, Graeber than Mao. I've commented elsewhere previously in another discussion about real world socialist projects that actually deserve the label rather than using it as statements of aspiration at best or for blunt populism at worst. But they all have in common that they don't start from authoritarianism because authoritarianism always poisons everything. It's difficult to find this information if you don't look for it because we exist in a culture shaped by anti-communist hysteria and Bolshevist propaganda both agreeing on using the labels of communism and socialism exclusively for flavors of authoritarianism. But learning always takes a little effort if you want to do it right.

[0] I'm saying "at that point" because there were genuine attempts to establish forms of communism in the chaos after World War 1, including a number of groups that were aligned with the Bolshevists. There was actually a lot of infighting in the German left over whether to support the Bolshevists or not that largely boiled down to "but they're doing communism wrong" versus "but they're the only ones successfully doing a revolution right now". Most of them died[1] either in battles with the monarchist Freikorps (which were also the breeding ground for the (NS)DAP btw), during violent clashes with other left-wing groups, or at the hands of the Nazis, either prior to their rise of power or thereafter.

[1] It's worth pointing out that despite the Weimar Republic having a central government, many judges would deem defendents not guilty of murder or assault when the act was done "out of love for the country", which specifically meant the monarchy. This largely gave the Freikorps and nationalist groups free reign whereas socialists would be sentenced if they did the same.

[2] The Nazis weren't very popular in Germany when Hitler came to power. The popularity came from the power and even then it was largely artificial. The reason you see cheering crowds in historical documentaries is because those were the scenes the Nazis wanted you to see. You only saw a fraction of the people but it was implied (or outright said) that "the silent majority" was on your side if you agreed with the Nazis. Once they were sufficiently entrenched in power, joining the Party was just an easier way to do networking for your business or your career. You'd do the salute somewhat ironically and both of you would be in on the joke of it, but eventually it stopped being funny but you still did it. Then you had to do it.