This is always been happening to some who do not have experience when it comes to the price of altcoins, Some other percentages of people are also bounty hunters who only want to profit, So after they see that their tokens and coins are on exchanges, Of course, they will sell it while still at a good price.
Because they (bounty hunters) are know that the price will immediately down when the other sell it, that's why they will not will not hesitate to sell their tokens and coins while the price is still good. Most of them only accept whatever value is obtained from the sale at that time, than the value continues to be smaller.