Because so far every communist state has been created by violent revolutionaries side stepping the democratic process. The type of people who join a party that wants to shove the beliefs of 10% down the throats of the 90% are inherently authoritarian. Its no wonder they never become real democracies once they have total power.
I believe is has to do with the competitive winner takes all economic system that these governments evolve within. It breeds distrust, which leads to authoritarianism.
The american colonies were not democratic, they needed a violent revolution to create a democracy. There was no peaceful mechanism for them to take power.
Russia and China were already democracies before the authoritarian parties took over. They could have peacefully taken control in elections if they were able to convince the voters. But instead they disbanded the legislatures and stopped having elections.
"Russia and China were already democracies before the authoritarian parties took over."
Russia was not[0]. One of the key reasons that laid foundations for revolution there was wide discontent of nobles and their arrogance towards common people.
The authoritarians (bolsheviks) didn't like the results (thought the people weren't conscious enough yet to be trusted to be democratic) and disbanded the democratic assembly. Instead they used their own assembly made of up representatives indirectly elected via small local groups where they controlled the voting by force. Which caused a civil war in which the authoritarians won.
The authoritarians were just more organized and better at violence.
An interesting history fact I didn't know -- thank you. But I doubt one election, which results were immediately negated anyway, is enough to call Russia "a democracy". It looks like it was just a (failed) attempt of bolsheviks to get an international legitimacy.
