There was an article last week with a bit more detail on the cancellation here: https://plus.thebulwark.com/p/jon-stewart-and-apples-low-reward
Notably, although it does seem that worries about political content vs China (and also possibly for some customers at home) may have been a trigger, the show really was not that popular which no doubt also helped the decision to cancel.
Despite The Register's claim in the article the show was popular, it seems the first season of the show was only getting ~40,000 unique views, with it seeming doubtful very many people paid for Apple TV+ just for Jon Stewart. Although the second season apparently improved a bit, for a claimed salary of "tens of millions of dollars" it's not surprising the show would be canceled even if there was no political concern (source: https://entertainment.substack.com/p/over-140-of-the-biggest-tv-show-flops?utm_source=%2Fsearch%2F%2522jon%2520stewart%2522&utm_medium=reader2).
The bigger concern (even though this show seems to have deserved cancellation) is that TV is a very small part of Apple's empire, and therefore they have no incentive to take any risks that might damage their business elsewhere. Having broadcast media as a small side gig for larger companies is really not great for honest reporting, but there were probably other reasons as well for this specific decision.