Good for them! I'm impressed with how quickly they were able to conclude their accident investigation and get approved for return to flight. Brings to mind all of the multi-year Shuttle accident investigations.
I suspect the reason for the swift return to flight is half that fact, and half that SpaceX is more bureaucratically efficient.
If it were to have happened on a manned flight, even with nobody was on-board during the test, then I doubt we'd be seeing return to flight so quickly.