Due to preaching of Muslims at that time which enters china through these western provinces.
Explanation:
Most of the Muslims of China live in the western province because to these regions the Muslims came from Arab to spread the light of Islam. Many people accepted the religion at the hands of Muslims at that time which we called them ''Sahaba'' or companions of the Holy Prophet Muhammad (S A W). This western province linked to the Arab so these companions of the Holy Prophet Muhammad (S A W) enters the country of china from this region.
