I think it is not true, no one can prove that it is really manipulated by any group of people company or corps, it is only goes down and pump again because of some investors large or small do buy and selling, that is why there is a movement of the price depending on the volume of selling or buying pressure, i think manipulation is just a theory base on what people think and not on the reality.
Why manipulation is not true? like just imagine if you are a owner of a project and your team is holding 30% coins in total supply, if your team is start selling all of those coins, that will not be highly reflected in the coin price? of course price will be crash, so it's simple thing about market manipulation which is very much true.Has any thief just stolen and shouted : "I'm a thief, catch me, catch me" ? Or is there any criminal who kills someone and then admits to being the murderer and publicly announces it to everyone ?
It is true that we do not have any concrete evidence of market manipulation but that does not mean that the market is not manipulated . Even the stock market with a capitalization of over $100 trillion has been involved in multiple market manipulation scandals , let alone a small market like cryptocurrency .