So in this case the trigger is the system is down and we need to understand how do we keep doing what we do as a group. But then when the main system is back, how do we keep them into the new one?
This goes back to the variation by generation and group interests. People that already feel oppressed by the main platform may likely stay on the one you provided them, otherwise most will go back to whatever they and their friends liked about their main platform. Unless these people are your employees it is unlikely you would be deciding where they go. Even in that case employees will do what they can do.
Ask these people what they like about the platform they are on and decide if you can replicate or enhance that experience. If you can, show them and they will decide if what you created is something they would prefer.