TLDW
China uses its trade surplus with the US and EU to build infrastructure risk-free by lending the surplus in Euro and USD to BRICS countries instead of buying US Treasury bonds. The loans are used to build infrastructure, such as railroads, which benefits Chinese supply chains. China can afford to ignore whether the loans are performing because the stability of their supply chain is more important.
I found a YouTube link in your post. Here are links to the same video on alternative frontends that protect your privacy: