Most people would say the global economy would die, for a short bit there might be some truth to that since supply cannot change in the short run. But in the long run the markets would shift production elsewhere. What is now made in China would instead be made in like Southeast Asia or India. Losing billions of people would mean less commerce though so the economy wouldn't be as good as if the Chinese were still there, but whenever there are changes the market always adjusts to them(assuming its allowed to) but at least the Chinese government wouldn't be a problem anymore.

A gigantic race to claim all of that fucking land and to rebuild the factories to resurrect the production

Unless the Land vanished. Rise in fishing industry?

there would be a massive initial shock, and that would probably lead to a depression that would last a while, but eventually other nations would start to manufacture themselves and IMO the economy would eventually recover