There is one word for that, "Manipulation" although I don't know the reason behind why they are keeping on doing that, And in my opinion, I think they are up to something or maybe they would let people think that bitcoin cash is doing great just like Ethereum did, Or this is just a publicity stunt so investor would think positively that BCH is recovering or entering the wave of increasing its value, This is just my conclusion regarding the sudden tallying in the price of ETH and BCH And I think they are not giving up yet.