Creator Michael Hirst explains his choice to cast Jonathan Rhys-Meyers as Henry VIII.
We felt that Johnny captured the essence of Henry. He portrays Henry in a way that shows him as a man while also displaying a regal quality. Which of course you need to portray Henry VIII.
Actor Jonathan Rhys-Meyers on his role as Henry VIII:
I understand that I do not look like Henry, but I have completely immersed myself into this character. I hope my hard work will show through my performance and that people will overlook the physical differences between Henry and myself.
I own the box set of "The Tudors" which includes bonus features. The above quotes are from interviews conducted with the show creator Michael Hirst and actor Jonathan Rhys-Meyers.