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 can be take over because crypto currency is open source and any one or any group can run it but what causes it to collapse is due to the dev's failure to transfer ownership and allow holders to take part in the development ,once the dev goes out no body will take over.