1. I think China want to temporarily crash the market so they can collect more BTC (and other coins dirt cheap) before announcing that they are officially adopting. At that point BTC (and other crypto) will sky rocket.
2. They don't want their citizens to trade cryptocurrency and earn (relatively easily) in fear of losing their cheap labor force. They will then try to make it as difficult as possible for it to flourish in their country.
Which is it???
It does not matter whether its a conspiracy or a fact. They have come to state that crypto currency trade is disrupting their financial system simply because they cannot control bitcoin. The moment that can be achieved by them either directly or otherwise, they will come back to their senses and every crash that have happened won't matter any longer again.