icos failed because of several reasons:
1. they are designed to fail in the first place. the dev team's sole mission is to scam people's money.
2. too much money raised from ico. this tends to tempt the dev team to just run away with ico fund.
3. lack of skills. many ico are offered in rush without proper preparation. this is a recipe for disaster.
4. lack of interested people to invest.
In addition, the lack of spreading information was also a factor in the failure of the ICO, as in this bitcointalk forum on announcement board, the new thread about new ICO will not be on the first page for a long time, so only a few people know the ICO