"we believe that the case is closed— supplementing the diet of well-nourished adults with (most) mineral or vitamin supplements has no clear benefit and might even be harmful. These vitamins should not be used for chronic disease prevention. Enough is enough."

The problem is that (specifically in US) most adults are very far from being well-nourished.

For example, https://en.wikipedia.org/wiki/Malnutrition "Overnutrition caused by overeating is also a form of malnutrition. In the United States, more than half of all adults are now overweight — a condition that, like hunger, increases susceptibility to disease and disability, reduces worker productivity, and lowers life expectancy.[51] Overeating is much more common in the United States, where for the majority of people, access to food is not an issue. Many parts of the world have access to a surplus of non-nutritious food, in addition to increased sedentary lifestyles. Yale psychologist Kelly Brownell calls this a "toxic food environment” where fat and sugar laden foods have taken precedent over healthy nutritious foods."