Ethereum price starts declining when ICOs started failing due to scam. We all know that majority of new projrcts us their platform that is why the demand for ethereum decreased. If this continue or if there is no further development on the ethereum's team part, ethereum might as well go down in ranking in regards to marketcap.
Thats not true ,failed and scam project is not really affect the price of ETH the ICO did. Since more of the ICO accepting ETH as investment and too many of them has been successful most of developers sold that raise fund and exchange it to fiat and each of those ICO affect the price of ETH more ICO success more declining of the price of eth will be experience.