First of all, I don't believe that someone who has millions and millions of liquid cash would sit around and watch the screen and look at the trends of crypto currency and pump it then sell it only to earn cents to the dollar. But there was, I'd think they would want to maintain the volatility of the market because that is where they earn.
Well, just as you have said, they will want to maintain the volatility of the market as you keep seeing it, and trust me most of what you see sometimes is bots at work, and they really do not have to sit on the chart all day.
Moreover, what whales do is emotional analysis. They look at the price zone where people are beginning to get greedy and they dump, and in this case, you will see some who really got into the market for the wrong reasons, panicking and trying to quickly bail out at loss, and these are the people that they target most of the time, and one of the reason why the only way this can be curbed is when we start seeing real life usage.