Planning processes from five years ago or ten years ago don't always get updated. And corruption is still a problem in China. Perhaps not as bad as, say, India, but still an issue. Which is to say, that not everywhere makes cost optimal decisions all the time.

Even the IEA, a huge skeptic of renewables, that consistently makes ridiculous claims limiting the potential for solar and wind, acknowledged that solar is cheapest:

https://www.carbonbrief.org/solar-is-now-cheapest-electricit...

Decision makers often have huge biases from past data and cultural influences. The bias against renewables and storage in the energy industry is absolutely oppressive. And in most infrastructure decisions, decision makers don't have to answer to shareholders about getting outcompeted by a smarter decision maker that made a better choice.