Because China (and Mexico, India, Southeast Asia, South America, Africa, and the Middle East) have not really introduced sanctions (except against military equipment)? These companies are following their government's policy, which is more than can be said for companies like PepsiCo and Mars (both American).

International trade is dictated by countries, not by companies. If a company is breaking the policy of the country it operates from, that's obviously very bad. These companies aren't trying to pick sides: their government hasn't picked a side and so there is no reason for the company to.