This underground complex wasn't destroyed by the passage of time. Signs of deliberate damage are everywhere: shattered objects, ruined murals.
But far as I can tell, the only dead are those buried in the sarcophagi. Whatever happened here all those centuries ago, it doesn't seem to have been a battlefield.
More like historical erasure. A battle of cultures, perhaps, or a new ruler ordering an uncomfortable truth buried before it festered and chipped away at the faith of his people.