Many monotheistic religious beliefs of today had polytheism as their roots. Peoples all over the world have at one time or the other believed in gods and goddesses before conversion to the major monotheistic faiths. Beliefs in gods and goddesses are still rampant in some parts of the world.
Unless we assume that at one point or the other many of the peoples of the world colluded to deceive humanity by inventing these creatures we must assume that they really exist. The universally of these beliefs must be taken as proof of their existence. Ancient peoples whose intuitive faculties were still refined could see and observe these creatures at work. Because of their different natures people began to fear and worship them.
The fact that we do not see or hear these creatures today should not be taken as proof that they never existed or do not exist but on the contrary must be taken as proof that humanity on the whole has retrogressed so far that we had lost the ability we once possessed. These creatures of course are not gods but are creatures of God who have their origin in the Animistic realm and whose activities are closely connected with the development of and maintenance of the natural world.
As man gradually opened himself in his gradual upward spiritual development, he had to go through stages which allowed him first to recognise the nature of his immediate ethereal surroundings; hence the first forms he saw were products of his thoughts. He carved images in wood of these forms and this is what is known as the worship of demons.
As he progressed he recognised higher entities, hence we have stories of the recognition of nature beings like salamanders, gnomes and so on. He went further until he recognised the highest of these nature beings and these are the gods and goddesses of the Egyptians, Greeks, Romans and so on.
His initial reaction was as he had done in the past was to make images of them and worship them. Later when his horizon widened further, he learnt to recognise a little of the spiritual realm but we still have not been able to clearly recognise this realm yet, as mankind of today do not even know what the word spirit really means. These so-called gods are still there today as in the past and still carry on the same activities as before.