I believe the following have occurred, based on skimming the relevant threads:
- sunbeam's hosting provider warned them about doxing
- the instance admin demoted the mod for this and other reasons
- the instance admin expressed an intent to leave the server
- discussions have begun to determine whether sunbeam will continue under new management or pull the plug
I suggest delaying a decision on defederating until the new management, if any, makes its position known.