liu made the trades on himself

he didn't represent any organizations when he made the trades. he made those trades via his broker from LME. Either some people weren't following the rule or there is a loophole somewhere.

China has no obligations to pick up his mess. Once there were talks about sharing the loss between China and LME.

Trying to show the world it's a responsible country and trading partner, China steps in to handle it now.

In a nutshell, China doesn't have to shoulder any loss incurred by the incident; unlike the japanese incident.