There are many reasons of dropping in price after listing some of them are
1. Bounty hunters dump their coin
2. High bonus on Presale phase
3. At the time of listing there is no such development of project which was told.
4. High ICO Price
I think the prize hunter is not very influential, the price of ICO falls because they are still in the development of their ICO projects, their products or services are still relatively new, someone who buys when the presale cannot get rich immediately when the ICO ends, they must follow the development of the ICO company, if the ICO company it works and has a customer, the price will rise.
the most important is the concept of the company, look for ICOs that have the concept of innovation that is a problem of society