My point is that they tried going after the big name actors, but since they don't have room in their schedules, they decided to instead find relativity unknown but promising actors to be cast instead. Would I have loved to see someone like Hardy leading the film? Absolutely. But I have faith in Black to deliver great performances regardless of name recognition.
Besides, it's been proven time and time before that a cast with big names doesn't automatically mean the film will be good and/or be successful.
And I would say del Toro is way more well known than Brody, as he's appeared in more high profile projects. This year alone he has Terrence Malick's new film Song To Song, the sequel to Sicario, Soldado, and Star Wars: The Last Jedi.