I have a theory. In fact, I have several. But let’s skip the more esoteric, and consider those with health implications:

Theory 1: Anthropogens, a term given to factors in the man-made environment that affect health, are like the ‘germs’ of chronic disease.

Infectious diseases began to be controlled only when germ theory brought infective micro-organisms together in a common bundle.

Modern chronic disease control has suffered from a lack of similar monocausal focus, leaving illnesses to be managed in silos called heart disease, cancers, respiratory problems etc.