I think why the token are drop because the bounty hunters are selling their tokens once they listed to the market so the ICO investor are losing some money becaude the price on the market is lower than the price that they purchased on the ICO.
What you say may be a common reason in people's minds but there are other things that cause it. Among these are the unstable market conditions, early investors have dump away the tokens because they bought cheaply with big bonuses and another small possibility is the DEV /team itself who has dump it away.