Imagine your community has gotten into a mess, it simply does not work anymore due to mistakes, wrong decisions, and wrong turns taken in the past.
But the general idea and concept of the community is still good and promising and the targeted audience is still out there. The corresponding niche in the marked of online communities is still there, waiting to be filled. Succeeding in doing so would make many people happy.
With hindsight, it is clear what went wrong and what should have been avoided.
So the idea is to some kind of restart or reboot the community without making the same mistakes again.
How can such a restart of the community be done without losing the trust of the target audience?
There are a few good people that should be taken over into the restarted community. Some good users have been present during a certain time but they could not be retained in the present community. It would be nice to see them again too.
There are also announcements and advertisements for the present community and in principle it might still be that from them, some people would like to join us, and they should be led to the restarted community too.
This question is somewhat related to How can I restore the focus of a community without driving away the userbase?, but just trying to refocus the community seems no longer sufficient or feasible.