I don't have the exact dates, but South Korea gets framed as having always been this multiparty liberal democracy when it was a right wing military dictatorship into the 90s.

People often want to frame North Korea as being behind, less developed, and whatnot, and will insinuate its inherent to its government structure. But, life expectancy, education, and economics in the North all outpaced the South while both countries were totalitarian and authoritarian.

Then, economic liberalisation in the south lead to a stronger economy that created the popular image of South Korea in people's minds today, meanwhile the Soviet Union collapsed, meaning that the North's economic security was weakened as it lost a trading partner and ally.

The metrics that people point to now as evidence of why North Korea is a "bad" country only came about within the last few decades, even though much of those same metrics have been true for capitalist countries for far longer.