You can’t explain why standards of life have been massively boosted in actually existing socialist countries
You can't explain why the same thing happened in Capitalist countries and doesn't appear unique to "socialism".
How is it possible that there are only “good dictators” in communist countries?
Most outright dictators in communist countries were shitheads. After Stalin died, the USSR had the secret speech. After Mao died, the Chinese communist party made it a high priority to prevent any one person from ever gaining that much power again (which fell apart with Xi Jinping). Ceaușescu was more interested in a life of luxury than in the working class. Most communist countries at most times had a political elite that ruled, not an individual with singular authority over the nation.