Less than 4000 BTC are not big to dump the market. One Binance, 173,200 BTC has been trading in 24 hours. How 4000 BTC can manipulate the 173,200 BTC in a day?
I can not step in the shoes of weak hands who panic sold their bitcoin but if you are considerting F2Pool as a cause, it is only a trigger (if it is). The rest activities on the market is manipulation game.