[cbhl]

Probably large fixed costs (engineers, builders learning how to do the thing) amortized over building a large number of plants.

China has been constructing a lot of new nuclear power plants over the last 15 years -- estimated at ~12 GW in 2013, but now closer to 50 GW as of 2021. Wikipedia says 50 plants as of 2021: https://en.wikipedia.org/wiki/Nuclear_power_in_China.

Anecdotally I've heard that temporary pollution control measures during the 2008 olympics gave the populace and decision makers a taste of reduced air pollution, and gave increased political willpower to invest in solar, wind, and nuclear power generation.