His authority strengthens his moral tone
1. Whatever Goole is, his unsettling presence might just be down to confidence. He knows how to create an air of uncertainty and reel everyone in
2. He makes sure everyone recognises that he's in charge
3. He takes control and leads the events. They're confused, but Goole never is
4. He "massively" interrupts which means that he cuts into the dialogue "with authority", e.g. when he tells Birling that Eric can "wait his turn".
5. His authority makes people take him more seriously and makes everything he says sound more important
Writer's Technique - It's worth thinking about how an actor might play the Inspector - maybe with his voice getting louder and louder as the play progresses