[MDPilot]

An educated guess would be that the aircraft was dispatched with one engine driven generator out on MCO. This would mean operating the flight with the other engine generator and the APU generator with the APU running the entire flight. When the other engine generator failed, the electrical system load shed the cabin and galley electrical items, leaving the APU generator to power the rest of the airplane (cockpit and other essential items.) Divert into alternate airport followed.