Most token falls in price when listed in exchange because of the following reasons
1) Bad Token matrix and higher % for Private and presale participants
2) Bad marketing
3) not able to prove their tokens real use case.

when the new token list on the exchanges these presale and private sell participants dumps token to recover their funds to get profit on their investment. you know what because of them some bounty hunter always get blamed, bounty hunters only get 1% to 4% of the total allocation of the token than how can they be the reason of dumping.