Well thank you for asking. You see as humans we have a craving drawn into our subconscious to have many things, but most prominently we crave logical understanding and society. You see before the rise of the monotheistic ideology words like "Daimon" were used around the world in many polytheistic religions, with its original meaning of a spirit with/of divine power. But as newer theological philosophers came up with this "logical" ideology of monotheism they had to spread their idea. Now while there are always though whom are looking for the 'new' thing to get on, and those who will follow anything due to their lack mental capacity, and of course those whom it made sense to, they still had to gather more people. Yet due to the large popularity of polytheistic religions they could not. Do you see where I'm going with this?
So to turn the tables to gain more power and lets face it; wealth also, they had to find a way of converting those of one religion to their cause. To do this they had to demonize the popular Gods, much like what you see in American presidential debates. So that is what they did, but what oh what to call them? Did you guess "Daimons"? Well congratulations! but this isn't a game show, I'm sorry. But you see now "Daimons" aren't "Daimons" anymore int he culture as monotheism grows. "Diamons" become "Demons" meaning now not 'Divine spirits' but for the churches use they are now 'Evil spirits'. Now its not just monotheism's fault, its ours as a culture as well. Through media and generational teachings we have demonized the Diamons. Due to families, churches, movies, songs, art, literature and so forth we have fueled this ill formed idea that what we now know as demons are evil.
So where am i going with this? Well lets get to the nitty gritty. Basically by this we can see that in the most basic and common terms 'Pagan God + Monotheism = "demon' but instead we should see it as 'Demon - Culture = God'.
Now I'm not inferring that ALL entities we know as demons are in fact gods, some are not friendly, just like any organism, or like any god. Some may ever be false, thrown in their by the church or some guy in his mothers basement. But i believe that most demons as we know them are gods (such as AMON from Ars Goetia is AMON-RA the Egyptian God) I've found that if you look in many books you'll find etymological connections to Pagan Gods.
Now i know that many of you already knew this, and I'm sorry if I wasted your time reading something you've already have known.
So remember when I said I don't mean to offend anybody? I meant it, so please do not message me that I offended you or your beliefs, I did not mean to do such.
I also apologize for anything I may have spelled incorrectly, it's late here.