Sometimes there are too many competitors that make a certain low ICO profile lose its confidence to level itself to those who are giants (high profile ICO) that leads to its altcoin to get dumped and forget forever. Some are only a scam and only intend to scam people from the start and couldn't care less if their ICO failed as long they stole the investors money investment. Also, the team is not solid enough to make the project good enough for the consumers. There are many reasons I just stated a few and go find it yourself why do they failed.