Was = past simple. A completed action in the past. "She left the house."
Had been = past perfect. A completed action in the past, that ocurred before something else happened. "She had left the house before he arrived". "She had left the house, so she never knew how the fire started".
I just would like to mention that the simple past is directly linked with a completed action in the past, that happened at a specific time, the speaker may not actually mention the specific time, but they do have one specific time in mind.