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.
While I cannot prove there is manipulation going on in bitcoin cash of all the coins that I analyzed bitcoin cash is the one that has the most extreme moves on average and while that may seem like something good, to me this seems like a sign that something is wrong and one of the possibilities for that is manipulation, the price of ethereum seems to me that is growing organically since people are interested in it because of the fork but in the case of bitcoin cash I have my doubts that is the case.