How does industrial melanism support Darwin's theory of natural selection?

Industrial melanism indicates the effect of industrial pollution on the population of moths. Before industrialization, the number of white-colored moths on a tree was greater than the number of dark-colored moths. The light-colored lichen used to grow on trees, and therefore moth predators could not spot white moths easily; thus, dark moths were fewer in population. But due to industrial pollution, lichens could not grow on trees, and then it became difficult to spot dark moths on the dark background of the tree stems. Thus, the population of white moths became less than that of dark moths. This process is termed industrial melanism. So, before industrialization, white moths were better adapted to nature, but after industrialization, dark-colored moths were more fit for the changed environmental conditions. This supported Darwin's theory of natural selection as, when the natural condition changes, the organism that is more fit for the environment survives better than others.