Jack Ma taught English at the university level [1]. He wasn't struggling for words, he's just not as smart as some had assumed.
[1] https://money.cnn.com/2018/09/09/technology/business/jack-ma...
[1] https://money.cnn.com/2018/09/09/technology/business/jack-ma...
For what it's worth this matches my own limited experience from the early 2000s.
Relevant from other comment:
> I don't know whether you've ever experienced a foreign-language class taught by a non-native speaker, but I've taken Academic Writing classes in English at a top Chinese university and the quality was terrible. English literacy is rare in China even though it is a mandatory subject, so the bar to becoming a teacher is quite low. Often, they'll have an excellent breadth of vocabulary, while being unfamiliar with many idiomatic expressions and cultural references that come naturally to a native speaker.