[How would it be possible for known billionaires to remove wealth from a communist country?]
A lot of the “corruption” cases are about wealthy people moving their money out. With the exception of Belt and Road and high tech acquisitions (and not even all of the high tech purchases), many of the corporate Chinese investments we keep hearing about aren’t actually “Chinese” - they’re investments by the controlling shareholders of these corporations rather than the government. And yes - that’s how they get their money out. Assets in countries that will give the Chinese government the finger if it tries to seize them (from the Chinese individuals who own them) are favored, which is why the US is getting so much Chinese money - a good chunk of it is entrepreneurs getting the heck out of dodge before the gangsters who rule the country get their mitts on their hard-earned money.