>release Attila
>nobody buys it, financial failure
>release Thrones of Britannia
>nobody buys it, financial failure
>release Troy
>nobody buys it, financial failure
>release Pharoah
>nobody buys it, financial failure
vs.
>release Warhammer
>huge success
>release Three Kingdoms
>huge success
Historical fans don't buy games, fantasy fans do. It's no surprise that CA are looking to other big properties like GoT, Star Wars, and Battlestar Galactica.