Charles Laughton was an eccentric British actor who reguarly collaborated with Brecht.
Galileo, on the other hand, was an outspoken and innovative thinker who was condemned by the Catholic Church for his beliefs about the nature of the universe. Laughton and Brecht saw Galileo as an ideal subject for the kind of play and presentation they were both interested in producing.
Brecht on Theatre: The Development of an Aesthetic