It is no surprise that dumping comes often when the project was just recently launched. And dump is being done by almost everyone who have bought the project, who made the project, who participated with the project. It's a combination of all those people who holds the token. But mostly, it's caused by the whales who are holding those tokens. This is becoming the norm for the newly launched projects, you become late to sell it then you'll miss the higher price that you should about to sell it. Also, check how much is the percentage of tokens from the total supply of the project is allocated to that bounty to think that the dump is caused by bounty hunters.