'We are all Thomas More’s children’ – 500 years of Utopia
theguardian.com
theguardian.com
Specifically, all of those regimes supported some form of "democratic centralism" and other aspects of Leninist party theory, such as the idea of a vanguard revolutionary party, which is not part of classical Marxism.
Amongst he first people purged by the Bolsheviks, were Marxists and other socialists that opposed their coup, and the resulting authoritarianism.
People who had spent months since the actual revolution, where power was handed to the Duma, building towards a liberal socialist society, and who won the vast majority of votes for the constituent assembly on that platform (the Bolsheviks won ~10% of the vote; hence the "October revolution", which was nothing more than a coup)
Many of them met their end for continuing to oppose the Bolsheviks politically, many after taking up arms and fighting on the other side in the ensuing Russian civil war. Some managed to flee.
I'm certainly enjoying the glorious capitalist utopia we live in today, where perfect market competition has eliminated all the old woes of human life! Why, if I can afford the loan payments, I won't even have to die of old age! /s