Wife's parents had a house built on a concrete slab with no rebar. Seems the city inspector looked the other way. You could be on one side of the house and look under the walls clear across the house. After we got married and would visit her house, we had to behave. Course we were just married then and that was not an easy task.
My bet is that it had no rebar or it would have held together without anything under it. Not enough weight there to break through with it.
Maybe the demolition was to cover up the fact that the hood was like my wife's and it was as said, bad publicity for the realtors.
Course the wife's folks house was built for returning GIs from the big war.