Why do you think good altcoins fail to keep going? It seems there are some that are good and people collectively have put in tens of thousands of hours supporting, but the team decides to give up midway.
a coin that failed was obviously not a good coin becasue a good coin means it should withstand all the things that you throw at it.
look at bitcoin for example. with all the things thrown at it with all the attacks, all the FUD and lies it has been standing strong because it is a good coin to begin with.