or Whales are selling to themselves first then they can get more cheap coin?
And they withdraw their coins to stake. Top 50 balances had a lot more coins (first had 8M+, now 2.4M), now on Bittrex less BT to trade.
Now selling orders has only 2 793 935 BT
https://beta.bittrex.com/Market/Index?MarketName=BTC-BT