Well it is either because the said project does not offer a unique usecase that people can cleary see and that has the potential to drive the future or the said team do not know how to do the right marketing. Because let's face it, hardwork is not enough to make a certain project successful. Try to look at those projects at the top, and if we will observe, we can see that it is the usecase, right way of marketing, transparency of the team, the community and a lot more that brings the project to a success. Hardwork is useless even if the people around you can see it. So it is more than hardwork.
What people need to understand is that in this market innovation is at the top of the list of the things needed to succeed, this is why all of those coins that are nothing but copies of bitcoin but that claim to be better never each any significant amount of success, as they are cheap imitations of an original project like bitcoin.