Say a group of rich investors got together and intending to buy huge amounts of bitcoin with the intention to one day crash the market. Say they told other investors of their plan deception and they bought into the idea. They done this for a while making the price of bitcoin soar. If they all collectively cashed in on their bitcoins and told people/ warned people and fooled them into doing the same via news articles, websites and other forms of mainstream exposure. Could they theoretically cause enough of a collapse to then buy the bitcoins back at a low price and wait for it to boom again makinf a huge profit or am I totally missing the point?
They can move the market but I think not that much because they aren't the only one now who is considered as whales.
If that plan is formed when bitcoin adoption is still not noticeable then maybe they can manipulate the market. But today, with lots of distributed coins from different person, the term market manipulation is slowly not fit to the movement of bitcoin price now. What those whales can do now is to try to make a panic like pumping or dumping big numbers of USD/bitcoin and see if the community will follow. If only numbers follow, then the attempt is failed.