It's because at the early of 2018 many projects are failed and some of the are scam. This is why investors are losing interest with altcoin and choosing bitcoin for long term investing
Projects are failed because investors are panic due to btc price crash, so they leave and take all of their investment.
I think if btc has reached it's trend again, investors will come back and investing their money into crypto projects
I don't think so.
Most of the ICOs are just scams and repetitive. There is no reason to collect user's money in projects like these. User's got bored of this and eventually lost interest in investing. This is how the ICO market fell.