It’s interesting that you felt betrayed by Miller not being the main character. In the book his chapters are a good example of unreliable narrator.
He comes across as a good guy and a good cop. It’s only later you realise he is unpopular which is why he was dumped with the Earther and his reputation as a drunk earned him an investigation they wanted done poorly.
Maybe the show got a similar result to the book in a different way.
I liked him too though and was gutted by his fate.