Germ Theory emphasizes the virus/germs as the foundation of all illness, and does not include the body as part of the theory.
Basically, Terrain Theory states that the more unhealthy a person is and the more out of balance their body is, the more susceptible the person is to illness, and the sicker they will get when they come into contact with germs.
Béchamp was the more brilliant thinker, but Pasteur had political connections, including Emperor Napoleon III. Reportedly not above “plagiarising and distorting Béchamp’s research,” Pasteur achieved fame and fortune largely because his views “were in tune with the science and the politics of his day.”
Meanwhile, mainstream medical historians relegated Béchamp’s ideas—not as attractive to conventional thinkers—to the intellectual dustbin.