From my own experience as an ex-christian and now a "pagan" person (syncretic demonolater), I'd point many factors that converged to a general understanding of how demons aren't so evil as we thought before (and how angels and God himself aren't so good as we thought before), while also leading to the understanding and reevaluating of the concepts good and evil, light and darkness.

Starting by the technological progress that allowed us to connect in realtime. Social networks, online communities that gathered people once unbeknownst to each other. Online platforms that connected people from different backgrounds, sharing once unknown knowledge. Books once distant from our reaches are now easily accessible through online libraries. Knowledge was never been so easy to reach (albeit there are many people that prefer ignorance).

This leads us to another important factor: the silent rediscovery and rising of ancient beliefs. The cyberspace brought us knowledge about the Sumerian faith, Hellenism beliefs and many, many others. Everyone can now know in detail about ancient deities and concepts in just a few clicks. Entities and deities such as The Mother Goddess (once extensively worshipped by our ancestors) is being rediscovered. We can easily know a Wiccan nowadays, or a Luciferian, or a neo-hellenist, or a Gnostic, or syncretic people like me, thanks to the internet connection and community. There's also the gnosis (i.e. knowledge through spiritual channelling) becoming available as soon as we have the basic openness to all this great knowledge and wisdom.

These two factors lead to a last factor: the weakening of Christiancracy (the former theocratic West where State and Christianity were intertwined as one) and the strengthening of both secularism (atheists, yet to understand how metaphysical aspects converge with the modern scientific inquiry; as an example, the modern chemistry began from the ancient alchemy) and syncretic ancient beliefs (once "pagan" and "forbidden" knowledge and both sacred and/or profane ritualistic practices, now openly available to be learnt and to be known).

In this way, movies and cinema are just echoes of these phenomena, echoes of the human awakening, becoming part of the culture, extending how the knowledge can reach and teach the masses, even though movies and TV series always have some degree of poetic freedom so they don't always represent things as precisely/concisely as a book/grimoire/oral knowledge. Media knowledge is far from perfect, but their esoteric and occult references spark the curiosity on part of the audience, people that will begin to really know what it's all about. As a personal example, I got to know some esoteric concepts through Supernatural TV series (although it demanded my own research that led me to Luciferianism and then to Lilith).

In summary, I'd call it the Aquarian Era, the Kali Yuga, the Revelation, the new Aeon. Some would call it "evil", while humanity as a whole can now rediscover what "evilness" really is: it's not the demons. It's a part of the Cosmos, it's a part of the Nature, it's a part of ourselves, as above so below. Our spiritual awakening is important to lead us to understand our own shadows through the wisdom of ancient, ambivalent forces, and reintegrating ourselves in Oneness with them.