These are dictators.
Stalin, Lenin, Mao, all dictators.
I don't even think they understood Communism except Lenin, but even he didn't really care about it as when he came to power he just basically became a dictator rounding up his enemies and killing them. If you wanted to understand Communism you went to Trotsky as he had the brains to figure out how to put it in place.
Same thing for Hitler, comes to power and rounds up his enemies and kills them.
Stalin just killed for the fun of it, he didn't give a shit about communism, he probably didn't even know what it was, only thing he liked more than drinking booze was laughing at his leaders as he sent their wives off to be shot.
Same thing for Pol Pot, they call him a communist, he even admitted that he didn't understand much of that stuff when he was in college, but what he did understand was how to kill men, women and children.
None of these guys are brilliant political intellectuals, they're just stone cold murderers.
When a government is coming up on the end of its life cycle all you get is authoritarianism with cops basically bashing people over the head because that's all it has to offer anyone and those are the only jobs available.