There is no conspiracy here (in my opinion) or attempt to flood the global market; but rather a giant internal economy (that most people ignored because China is kinda enclosed in its own bubble) is now getting exposed and it's showing how far China has come.
Another one is rails: China makes a lot of rails. A shit-ton but since these can't be sold to consumers, China created the "belt and road" thingy so that they can export their production.
China has a lot of excess capacity. They can out build the West, the developing world and India. They were just busy building inside but now that they need new export markets and have mostly finished building inside, they are looking outward.
The next few years will be interesting.