I think that one of the reasons why the Ethereum market cap has grown so much, and now it is decreasing so much, were ICO projects.
They accumulated large amounts of ETH, which at the time when the price dropped, they had to exchange to fiat money in order to be able to continue the project. It helps a lot in drops of price and market cap also.
Good times for ICO will return and Ethereum market cap again will grow high!