It isn't that hard to figure that out even if you don't have actual evidence. Logically, if you have enough coins to manipulate the market to your advatage, why won't you? And i think there have been several instances where a single transaction from the same wallet address bought or sold enough coins to move the market.
Come on lets not forget the event of December 2017.
How many of you really believe that it was the natural pump and not the artificial one? I am pretty sure that was act of Whales where most of the powerful came into the market with clubbed offer and made those dramatic changes. Im not sure why, but I always believe that event was product of artificial manipulation made by whales.