Economics/finance is obviously not my strong-point to say the least but can someone explain simply to be at a big picture level :
Everyone knows about the US Petrodollar hegemony and the now Infinite QE and completely abandonment of restraint in terms of printing cannot go on forever, in fact that it went on for this long is due to the fact that US military might have kept all the rest of the world in check, those that went off on their own route (Iraq exporting oil in Euro etc) got regime changed and you know the story...
For obvious reasons, other than nuclear WWIII or some other equally wild edge cases, the US cannot regime chance China or Russia even if/though China will eventually de-dollar itself with the digital Yuan or whatever other methods, I would say to some extent BRI is about China becoming less dependent on the trading in US dollar system, hedging against a potential US naval blockage in SCS, and also exporting to other developing countries China's expertise in construction/etc since it has overcapacity and China's own infrastructure growth cannot continue domestically at such rates forever etc...
By the numbers US is no longer China's largest trading partner and vice versa... and since US is printing literally like there is no tomorrow, China's holdings in USD is becoming increasingly more worthless... I read somewhere after the 2008 crash, Russia tried to get China to abandon the dollar right then and there but China felt it wasn't ready yet, and instead came to the US rescue, thinking that it would have leverage over America later, but Obama /US tricked China because afterwards they did a lot of QE and QE never really stopped, which means it basically diluted China's investment and negated any of the expected benefits/leverage that China would have down the road...
So now there are talks that US might kick China entirely out of the SWIFT system.... this would be a rubicon crossing type of event to which there is no going back... After this, either long term dollar will crash and USD will no longer be the world reserve currency, or if America can get enough of the rest of the world to side with it in abandoning and isolating China (much like how as it turns out US/Trump was able to convince EU/UK to reverse its earlier decisions on accepting Huawei 5G etc) then instead of Petrodollar ending, it will be China that will suffer another century of humiliation etc...
So my question boils down to this, given the above premise, why is China still basically making good for the US for pennies on the dollar (or even worse, since the dollar is fake since either Infinite QE will mean it loses all value sooner or later, OR US will freeze China accounts, force reparation for COVID excuse, and/or something like saying it no longer honors the debt it owes to China etc) and basically giving US stuff for free, when it can transform its own domestic markets, give UBI to its own Chinese citizens so that they can afford to purchase more of the goods that they produce for the West, and directly raise their actual quality of living/ living standards instread of the trick down roundabout way of making things for th West for free in hopes that it will help China someday?
