No Kidding, I'm A Man

In The Danish Girl, Nicole Kidman will play Einar Wegener, a 1920s transsexual, and Gwyneth Paltrow will play his former (or should that be former his) wife.

I can see why Kidman would want the role. It's an actor's challenge. Felicity Huffman won a lot of awards playing a transsexual in Transamerica.

But I have to ask who decides which direction the casting will go? In both these films, a man decides to become a woman. In both films, a woman plays the role. Were men considered? Who'd be more convincing as a transsexual?