There a lot of factors. But, these maybe will help you to know many.
1. Bad preparation before helding ICO. They don't prepare the team, announcement, website, roadmap and WP.
2. Bad strategy and marketing. They don't counted well the token allocation and fund allocation. They give so lot part of token to airdrop and not guaranteed to buyback them.
3. The goal of project is not ambitious. Their goal not look so ambitious, not unique because it same with some project that solve same issues.
4. No detail information about project can be found. They not write about their project very details and the team can't or won't answer some necessary question.
5. They not build their community. They only rely on airdrop to build the community, it's makes the community only have big quantity not on quality.
6. Restricting some country which have very big potential investors such.
7. Expensive price on ICO and have a lot of minimum on investment.