There is no benefit for the "big" whales to move the price. Usually, market manipulation is done this way:

Buying the asset and advertising to retails to buy at the same time, the "whale"  will drive the initial stage of the pumping, then it is the market ( retails ) that keeps pushing the price up. Then whale sell ( dump ) the assert to take profit. Or do the opposite:

Selling the assert and make the publich think the same way and selling as well. Then buy the asset back and pump the price again.

However, in Bitcoin, it is very hard to do the important part: advertising to retails. It may work in alt coints, such as SOL, it will never work with Bitcoin where there is no advertising department at all