Scam projects killed ICOs and make the legit ones to struggle with raising the money needed for their project to take off, and that's the unfortunate situation.
Another reason for the decline of ICOs are the banality of ideas. Everyday we see different projects with almost the same idea as the one before it. No matter how good the advertising is, if the project's idea is a fail in the first place, it wouldn't have a chance of succeeding.