We always see the price rise for a short period after the listing in the exchanges or after IEO, but soon price be come down,
this may due to two reasons:
The first reason is that the coin or token has no real value.
The second reason is the large sale of those who got his coin free such as airdrop.
Isn't that true?
Most tokens and coins, on their first instance of getting listed on an exchange, appreciate in value.
If a particular token or coin goes the opposite direction after a listing then it would suggest that investors have very little confidence in the project and does cause concern about the long term potential of the coin.
It could also just be a coin with very limited liquidity that has been overvalued in the OTC market. That could also be a possibility.
So it would be to blame for the fact that the token simply has no value, which is why investors do not trust and withdraw.
I don't know if I understand correctly what you mean by "overvalued"?
I would say that the worst mistake for ICO projects is bad tokeneconomics. If developers allocate too many tokens for marketing and do not secure it in any way (for example, by temporary lock), partners and other people not associated with the project will want cash out right after listing on exchange. This is where the immediate price drop usually comes from.