There was a certain question an atheist once posed to me. I gave him an answer. Then checked my answer years later with a Chabbadic Rabbi and a Conservative Rabbi. My question and the answers don't matter much, but the Chabbadic Rabbi, as part of his answer, said that this part of the creation is filled with base, low energy. Part of our purpose in life is to elevate and sanctify that energy into something higher, something holy. As one example, that's why you take an everyday event, like eating. Even animals eat. But when you say a Bracha, or a prayer, a thanks to G-d before you eat, you turn the base act of eating into something holy, something of high, spiritual energy. And it's through many little acts of this kind that we eventually will elevate the lower energies of this world.

So if the Satan or darkness seems to have its way in the world, my guess is that the world is mired in low energies, and we have to individually elevate it a little bit to raise the overall energy to something positive.