Because their intention for developing new projects is not strong, so if they already get people money, they will stop it. This is the fact of many new projects, that's why it is so risky to invest in a new project because we don't know the real intention of the team.
What kind of Crypto project you are talking about? At this moment, most of project belongs to defi, which has great hyip in market.most of those project launching from uniswap exchange, raising fund from token sell and successfully available in market! Although they scam later but Because of defi hyip, others project can't do well for their token sale, maybe thats why they have to stop their work
The Op questions are not specific, it doesn't matter Defi or non-Defi