It is probably a combination of a huge local supply chain, specialist labour, and relative low cost (energy, wage, land ...). Even German automakers are having

It is probably a combination of a huge local supply chain, specialist labour, and relative low cost (energy, wage, land ...). Even German automakers are having their electric cars made in China. The article mentions: "Among the posted positions are managers and engineers to supervise the operation of its 6,000-ton die casting machines known as Giga Press, one of the world's biggest." If you have a machine like that, your primary concern is probably not how low a wage you can pay, but rather finding people who can make the machine run as much as possible with few errors and without breaking it.