Sometimes when a coin pumps hard and starts to dump, novice will panic sell due to fear or other reasons, while the whales will buy up the dump and mop it all and then pump it even harder....
But, you have to think about the other possibilities such as cut losses or even it's just a bait to buy on dip. Sometimes it's better to do cut losses when occasionally the price at the end keep dumping because some stuff occurs during that time. There is no exact
absolute way to trade when the dump thing happens, it' depends on the situations.