Capitalism hasn't been a straightforward "savior" for failing socialist/communist societies—often, the transitions were forced by internal collapse, external pressures, or reforms blending elements of both systems. Here's a quick historical overview based on key examples:
Soviet Union (1991 collapse): Decades of central planning led to stagnation, shortages, and inefficiency. Gorbachev's perestroika introduced market reforms, but full transition to capitalism via shock therapy under Yeltsin caused hyperinflation and inequality. It "saved" the economy from immediate implosion, enabling growth in the 2000s through resource exports, but at the cost of social upheaval. (Per web sources like Investopedia's capitalism vs. socialism analysis.)
China (post-1978): Mao's communes caused famine (e.g., Great Leap Forward, 30M+ deaths). Deng Xiaoping's "socialism with Chinese characteristics" incorporated capitalist markets, FDI, and private enterprise, lifting 800M out of poverty. Still authoritarian, it's hybrid—not pure capitalism rescuing pure communism.
Eastern Europe (1989-1991): Soviet bloc countries like Poland and East Germany faced debt crises and black markets. Velvet revolutions led to market liberalization; EU integration provided capitalist aid (e.g., Marshall Plan-style funds). Growth followed, but with privatization scandals and inequality spikes.
No universal "salvador" pattern—many such societies (e.g., Cuba, North Korea) persist without capitalist shifts. Transitions often involve pain before gains, per economic histories.