Most developers have only one vision which is making money that is why many coins doesn't grow and they failed because they didn't see the vision ahead.
After they gather huge funds from their investors, they are more likely to conclude their project and stop developing or updating it. to keep their community alive, they will keep updating them with news and some false promises which they don't have any actions or plan to really do it in the first place. they also keep changing their road maps which doen't really make sense and finally they will dissapear with their investors money. Most of the time, this is how the pump and dump coin works, so you really need to be vigilant to avoid them.
Unfortunately this is true, many developers are not interested in creating a long lasting project out of their coin, and there are many reasons for this, like being to difficult, being unable to do so and too much competition, so as soon as they gather enough funds then they decide to just forget about the project, but in order to not look like complete scammers they simply delay their exit and make it seem as if the project just died naturally, even if they were the ones to kill it so they could just move on and create yet another coin or begin to spend their ill gained profits.