Dumping may be neccesary for some invedtors if they are in need of tgeir fund, they may decided to sell at any price and come back to buy back when they have sorted themselves out. There is no harm to anyone in doing this, cryptocurrency us an open market!
Besides they need money, of course they think that their coins have no future, they are worried that if prices continue to drop and are worthless, this has happened to hundreds of coins and tokens that made them worried about the coins they had.