Revolutions aren't great, period. But they happen when the system can no longer function, unless somebody carefully guides a transition to another stable state.
That said, wrt "communist" revolutions specifically - they result in totalitarian dictatorships because the Bolshevik/Marxist-Leninist ideology underpinning them is highly conductive to that: concepts like dictatorship of the proletariat (esp. in Lenin's interpretation of it), vanguard party, and democratic centralism all combine to this inevitable end result.
But no other ideological strain of Marxism has ever carried out a successful revolution - perhaps because they simply weren't brutal enough. By means of example: Bolsheviks violently suppressed the Russian Constituent Assembly within one day of its opening, as soon as they realized that they don't have the majority there. In a similar way, despite all the talk of council democracy, they consistently suppressed councils controlled by their opposition (peasant ones were, typically).
Bolsheviks were the first ones who succeeded, and thereafter, their support was crucial to the success of other revolutions - but that support came with ideological strings attached. So China, Korea, Vietnam, Cuba etc all hail from the same authoritarian tradition. Furthermore, where opposition leftist factions vied for dominance against Soviet-backed ones, Soviets actively suppressed them - the campaign against "social fascism" in 1930s, for example, or persecution of anarchists in Republican Spain.
Anyway, we don't really know what a revolution that would stick to democratic governance would look like, long term. There were some figures and factions in the revolutionary Marxist communist movement that were much more serious about democracy than Bolsheviks - e.g. Rosa Luxemburg. They just didn't survive for long.
That said, wrt "communist" revolutions specifically - they result in totalitarian dictatorships because the Bolshevik/Marxist-Leninist ideology underpinning them is highly conductive to that: concepts like dictatorship of the proletariat (esp. in Lenin's interpretation of it), vanguard party, and democratic centralism all combine to this inevitable end result.
But no other ideological strain of Marxism has ever carried out a successful revolution - perhaps because they simply weren't brutal enough. By means of example: Bolsheviks violently suppressed the Russian Constituent Assembly within one day of its opening, as soon as they realized that they don't have the majority there. In a similar way, despite all the talk of council democracy, they consistently suppressed councils controlled by their opposition (peasant ones were, typically).
Bolsheviks were the first ones who succeeded, and thereafter, their support was crucial to the success of other revolutions - but that support came with ideological strings attached. So China, Korea, Vietnam, Cuba etc all hail from the same authoritarian tradition. Furthermore, where opposition leftist factions vied for dominance against Soviet-backed ones, Soviets actively suppressed them - the campaign against "social fascism" in 1930s, for example, or persecution of anarchists in Republican Spain.
Anyway, we don't really know what a revolution that would stick to democratic governance would look like, long term. There were some figures and factions in the revolutionary Marxist communist movement that were much more serious about democracy than Bolsheviks - e.g. Rosa Luxemburg. They just didn't survive for long.