This is a "Wild Mass Guess" entry, where we pull out all the sanity stops on theorizing. The regular entry on this topic is elsewhere. Please see this programme note.
Earth is secretly the home of a society of intellectuals who faked a disaster to get all the idiots, trigger-happy sociopaths, and misc. crazy people off the planet, effectively making Earth Outside the Asylum
Granted, moving the elderly to Mercury was a huge mistake in hindsight