Chinese miners have been having trouble selling for the last two months resulting in a supply crunch on the market. Once they go insolvent and the BTC they haven't been selling gets liquidated or when they get their problem with the Chinese authorities sorted, there will be a flood of BTC on the markets because the Chinese miners have a backlog of power bills to pay.

https://www.coindesk.com/bitcoins-rally-supply-crunch-in-china