well basically there are a few reasons:
1) Nazism is higher on the authoritarian scale than Communism, when both are the epitome of authoritarianism, and if one had to be worse than the other, it’s communism, not Nazism. Nazism has its place in history’s greatest evils because it was an authoritarian plan that was instantly aggressive and clear about what it wanted. Communism, on the other hand, has also been very aggressive (look at its death toll compared to Nazism), but it’s actually been far more sly and manipulative. Their supporters take over education in many countries and convince the mob that their idea is good for the people easiest to victimize, thus making the successful feel guilt-tripped into supporting them, and the unsuccessful riled up into voting for them so that things will be more “fair”, a promise they never deliver on. They kill dissenters just like Hitler did, and even take over countries when the government is failing, just like Hitler did. Lenin and Mao both did this with Russia and China. An example of the slyness pulled off by these people is that Stalin actually instigated World War 2 by intentionally allowing and even encouraging Germany to sack Poland when he could have stopped it, because he was trying to get Germany to fight England (because England always protected Poland; it was how they entered WWI). Also, one of FDR’s advisors was a secret spy for Stalin, who used FDR constantly until a few months before FDR’s death, when he finally figured out Stalin was not on his side.
2) Nazism isn’t rightism, that’s just a lie made up by leftists so they can pin evil on rightists, since everyone rightly understands Hitler to be one of the greatest evils in history (though if you look back into the ancient days, Hitler-like jerks were actually quite common). And Mussolini (the Italian dictator in WWII) was a devout Marxist, placing him on the far left.
3) Anyone on the far left that says they’re libertarian doesn’t know what leftism is, and they’re probably a liberal that doesn’t know they’re not leftist (because leftists took over the Democrat party from liberals some time ago, which is why some liberals are now voting Republican. Basically we used to have a majorly liberal vs conservative country, and now the majority is leftist vs liberal). Liberals and conservatives tend to be the ones who want the freest country, and the left does not have such agendas.
i can’t see too much else because it’s blurry, but those are some