From the Chinese graduate students and professors that I have talked to the problems seems to be that it is really is to commit fraud and get a way with it.

In particular in some fields you can get rich writing grants, getting a considerable amount of money and writing fake papers.

There is a heavy temptation for many to do the same when all of their colleges are able to buy multiple houses and live an extravagant life style. An example from ~5-9 years ago would be a Chinese professor flying to California and buying a multi million dollar vacation house in cash. This is an extreme example and was uncommon even at the time.

My understanding is that this is not the case in all fields, it is easier to get a way with fraud in the less hard sciences supposedly. I also have read about several efforts over the last several years to try and correct matters.

It is also the case that many papers written by non-native english speakers suffer from grammar and spelling errors. Unfortunately incorrect grammar and or spelling often has a negative halo effect for many on the scientific content of the paper.

There is plenty of good science that comes out of China, however it suffers from a negative halo effect from the above sources.