It was famines caused be authoritarian leaders doing crazy things because they believed their ideology was more important than science and pragmatism. They were wrong and millions of people starved.

Socialism can become authoritarian oligarchies very easily they just have to put a thin coat of paint of ideological rationalization on it. The failures central planning in a socialist system has the same effect as the failures of the central planning of a small group of oligarchs in a capitalist system.

The rational solution is the dismantle the oligarchy, not replace the oligarchy with another oligarchy.