From the prospective of somone who never live in China before, my theory says mainly two reasons, 1) China has massive pool of players and as a results able to maintain the level of competitiveness that no other badminton nations (Den,Mal,Ind,Kor) are able to match. The players have to constantly show results to survive LYB. 2) LYB. Not my favorite coach but have to say team China's success and LYB is not purely conincidential, there must be a corelation there. The matter of fact is since LYB's became a coach, team China has been showing lighting speed improvement year after year. You can not talk about LD alone without adding LYB to the conversation.