Could anyone please explain me why we use past perfect instead of past simple before “that” in the sentence below? As I understand, we use past perfect in a sequence of events to show that the action expressed with that tense was before the other one, expressed with past simple. In this example, I do not understand how the fact that something was proved could precede the thing it proves. Should not it be expressed with the same tenses?
Her business had proved that it was possible to be sustainable and profitable at the same time.