Why do you think this kind of private detective fits so well within the film noir context?
I think Powell's portrayal of Marlowe is I believe a prime example of the film noir protagonist. This is an important distinction because the noir detective is part of the narrative and integral character and not some sort of Deus Ex Machina, like Holmes or Poirot. Marlowe is hard boiled and world weary, but also very clever. He's not just a 'peeper' or gumshoe trailing wayward husbands or wives. He makes valid deductions such as the "Do you do your own typing?" exchange between Marlowe and Ann Grayl