I think why many altcoin projects have failed because they only sell coins and give some bonuses to each buyer through sales, but they don't offer a long term program that they will do in the future. because I think many investors are interested in projects that have long-term prospects by launching various programs and products.
Actually, bonuses in the selling phase aren't a problem as long as the project has a long-term program that can guarantee for the development of the project and the token value. Sadly, as you know that many new projects only focus on marketing for the selling phase. They prioritize only for selling all their tokens as much as possible. Even worse, if the project has no product offered for a long-term goal. We simply can guess that the project will fail or won't survive a long time.
a big sale with lots of investors but the product isn't marketed or isn't in demand. then after the coin is registered the price will be destroyed. many investors withdraw their money from such projects.
they are strong and busy when selling but they are weak in doing project updates. especially in their community management. if investors are disappointed of course they can withdraw their money quickly. and many new projects make mistakes like that. not to mention projects that have to compete with projects that already have a strong market. Of course, gaining investor confidence will be difficult.