I'm sorry to say I was cynical and doubted they would last.
You can't force a community to happen. I never followed Voat but I did give imzy a chance and the feeling was very much that they were trying to force a community.
Personally I think the best chance of building a community is to build it around a service. Look at reddit and imgur for examples. They both started out offering a pretty specific service to users but grew into communities because people could use the service in a social way.
I believe there are other examples of this but mentioning instagram feels silly since they're now owned by THE largest community. But it's the same thing, they were a photo website and now every 13 year old is there.
I'm sure there are more examples of this. Offer a service to people, something mildly useful or entertaining, and attach a social aspect to it and I'm sure you'll get a community to spring up.