Normally a lot of factors play roul in the price of a token after ico.

1. Big invester who invest and buy the token with at lest 50% bouns. So this like to get back part of thier invest monye fast so they sell the bouns they get and after this they buy it again from a very low price.
2. Bounty Hunters

Some fear the dump so they sell fast and i feel this is a big mistake as long as if you do bounty hunting that mean you belive in project so insted of sell you hold.

For me i never sell fast i like to hold for years.