The same article could be written about many things China produces, not just solar panels and batteries. China spent decades learning to dominate in high-volume, low-margin manufacturing. They developed massive economies of scale, and lots of manufacturing expertise, both of which translate to labor efficiency that other countries can’t match.

The article also quietly mentions the fact that China has an abundance of cheap coal to power all those factories. That’s a big part of its advantage in “Processing $” in the third figure.