Probably they used to be able to keep the poor, poor via something brutally effective and simple, like only a tiny minority even getting the chance to go to decent schools or universities. Now they need a lot of wasted effort to convince people that the people at the top are working really hard and deserve it to maintain the same elite dynamic.

evidence: 7% got to tertiary education in 1975, and recently peaked at above 100% (not sure how that works to be honest, but the trend is clear)

https://data.worldbank.org/indicator/SE.TER.ENRR?locations=K...

More evidence: https://en.wikipedia.org/wiki/Economic_inequality_in_South_K...

Might a contributing factor be the older generation saw in their lifetime the change from extreme poverty to relative wealth brought about by the industriousness of the population?

https://en.wikipedia.org/wiki/Miracle_on_the_Han_River#/medi...

Probably population growth, less resources more people.