It's a protectionist move. It makes foreign products harder to buy, encouraging everyone to buy local instead. It also makes it easier to export, albiet at the cost of some profit margin. For a big, diverse economy like China's, it would be the smart play no matter what your ruling ideology is, which is precisely why the "free market" ideology of American hegemony is so strongly opposed to it.

almost all currencies have to be "manipulated" because the dollar is heavily manipulated. if you dont weaken with it your export industry gets fucked.