That's actually most often happened after launching on the exchange, were most of them are selling their tokens immediately due to majority of the traders in the market they want money. But other traders they do sell it also because they knew the price value of the token will get dump rapidly, then in a long run they will purchase again, which is a good methods anyway. But sometimes its not happening instead of falling its price the token value is suddenly increase or pump, were most of the sellers get regret on selling their coins at once. So if you don't want to encounter  regret in the end better to hold your token for awhile.