Inheriting his mother's imagination and creative brilliance, he developed the entrepreneurial business idea. On 12 April 1937 the company was registered at the Chamber of Commerce of Perugia as a sole trader.
In 1943 Spagnoli Angora was recognized as the largest and most modern industry in Europe in its sector: with 525 employees and 8,000 angora breeding farms. In 1944, despite the destruction of the establishment, the company was able to successfully overcome the crisis of war.
Mario used effective propaganda to diffuse the breeding of the Angora rabbit, so as to increase the number of Italian farmers in the early fifties to about 20,000.
He formulated the City of Angora project, a production efficiency model based on meeting the needs of the workers. From a simple place destined for production, the company, surrounded by the employees' homes, would become a self-sufficient community, organized and equipped with facilities such as a nursery school, afterschool, church, sports and leisure facilities. Although the project was only partially realised, it helped to strengthen the bonds between the company and its employees.