This is not specific to China but many larger countries who are good at other sports but they don't do well at soccer. Australia is very good at Rugby, Cricket but their soccer team is average and they make it to world cups only because of limited competition in their confederation (OFC). Domestic soccer leagues are just picking up in China. They mostly comprise to Chinese players and/or end up with retirees of European clubs (Retired Andre Iniesta of Barcelona/Spain moving to some club in China).