Couple of points.
The Bolsheviks were defeated in the polls by other Marxists, between them the Marxists got like 75% of the vote so Marxism (though not under Lenin) had a popular mandate.
To be fair to them a core theme of Leninism is the overthrowing of the political order by force, so I don’t think the Bolsheviks ever claimed to be freedom lovers.
Would the Nazis have been defeated if the Soviet Union hadn’t existed?
Would the Nazis have come to power if the Soviet Union hadn’t existed (they traded a lot on fear of communism)?
So was the rise of the Soviet Union the most important event in the 20th century?
Soviet Union & Nazis only came to be because of WWI.
So is WWI the most important event in the 20th century?
You could argue the Balkan wars caused WWI, they in turn were caused by the breakup of the Ottoman empire.
So is the breakup of the Ottoman empire the most important event in the 20th century?
The breakup of Ottoman empire led to Austria’s annexation of Bosnia and indirectly to the Balkan Wars. It had been prevented from doing this several times in the previous 50 odd years by Russia, but Russia was in a weakened state post the 1905 Russia-Japan war, so Austria felt it could act. So is the 1905 Russia-Japan war the most important event in the 20th century?
That’s the great thing about history it’s so intricate. Without the 1905 war between Russia and Japan you could argue there would be no Nazi’s and no Soviet Union, and of course you couldn’t stop there.
The Mensheviks hadn’t the cojones to do what needed to be done to fillet the Bourgeoisie. It all went wrong when they went with Stalin rather than Trotsky after Lenin died. We’d all be living in a free egalitarian communist paradise if it wasn’t for that.