When Michael Mann restored Thief into stunning 4K for its opening showing at the Aero Theater in Santa Monica, Mann made a number of interviews shedding ever deeper light onto the roots of his filmmaking. Respecting the fact that these articles belong to someone else, I am just posting the links. The first is a Q&A with Michael Mann, discussing not only Thief but the filmmaking process. It makes fascinating reading.
There is a less in depth interview here: