James Norton is not cast in Hamlet because he is the only actor who can speak the lines or embody the prince's fractured mind.
He is cast because he is a recognizable name attached to a body that has already moved audiences in other properties. Which reduces the financial risk of staging a play written 425 years ago that has been performed perhaps ten thousand times in English alone.
This is not a secret. It is the operating principle.
It says: repeat what worked before, but with faces we have already monetized. Ostermeier is a serious director, but he will stage Hamlet with Norton because Norton reduces friction in the financing process. This is how cultural capital becomes indistinguishable from financial capital.
The real tension is not between art and commerce — every production is both. The tension is between the claim that Hamlet still has something to say and the reality that the institution has stopped asking new voices to say it.
Find a performance of Hamlet by an unknown actor in a fringe space—a community theater, a university production, an experimental venue—and watch someone without a Netflix contract interpret the role. Notice what gets said that the prestige versions skip.