What failed in Russia and Eastern Europe was not communism or socialism, in any sense that this was understood by Marx or Lenin, but a bureaucratic and totalitarian caricature. Lenin explained that the movement towards socialism requires the democratic control of industry, society and the state by the proletariat. Genuine socialism is incompatible with the rule of a privileged bureaucratic elite, which will inevitably be accompanied by colossal corruption, nepotism, waste, mismanagement and chaos.
The nationalised planned economies in the USSR and Eastern Europe achieved astonishing results in the fields of industry, science, health and education. But, as Trotsky predicted as early as 1936, the bureaucratic regime ultimately undermined the nationalised planned economy and prepared the way for its collapse and the return of capitalism.
– From The fall of the Berlin Wall