I think this phrase comes from belief in the idealism of goodness, as for example in Plato and Confucius, at least as concerns human conduct, meaning that in the context of composite beings such as nations, cities, various associations and, significantly, the single person with his own will and action, evil is confusion as to how composite beings function best.
What is best? To be in strong contact with the “Idea of Good”. Now one may take this to be just word-play nonsense and believe, with Thrasymachus in The Republic, that everyone truly desires the pleasures of totally selfish actions, but in practice few achieve them fully, simply because they are not strong enough. So they idealize their weakness into a pursuit of imaginary and false “higher goals”.
But there are counter-arguments:
a) Satisfaction based on selfish possession of material things is, in varying degrees, enmity-provoking. So this kind of satisfaction goes together with an anxiety to keep it alive.
b) There are things, such as knowledge and creativity in art and science, that are attractive and durable and, unlike material things, can be owned and developed by many, simultaneously and without conflict.
c) An evil-doer will realize that his desire may be unlimited, but his practical power is not. (This is crucial, but I’m not sure how it can be proved theoretically. In practice it seems self-evident). This will be a blow for his ego. He will need some assistants. So a composite structure is formed, in which the evil-doer will eventually be in conflict with himself, as he will always need the assistance of those he would like to destroy. In this way, he may gradually realize that there is something in the nature of composite things that is impossible to overcome, and that those “higher goals” are not the false aspirations of the weak, but the true specifications of the best functioning of composite beings: co-operation in learning & beautiful construction. And the more he realizes it, the more his vitality will unify the personality split that urges him to be good in some respect and evil in some other.