Of course they do that.the whales have enough investments to play with the market.
when they want to dump a coin they sell some of their own , and to pump a coin they make some buy wall in market.
other people work as they want.
Of course big whales traders do it but it is a good for us, and also you and me, not a big whale but we are also a part of this game, and we also do it when bitcoin price pump then we sell our bitcoin and make profit and when bitcoin price dump then we buy the bitcoin. So enjoy this up and down and make profit in this wise, and now bitcoin pump is starting and it will be chanced for us to make profit from it.