I think the evolutionary growing intelligence of mankind inherently started for man to think about why and how which he saw and experienced came about, the answer most ancients came up with is that supernatural beings in the massive heavens made and was the cause of what they saw.
Many people today still think this to be so.
In a materialists reality the ancient mind was not the originator of the response "supernatural beings did it”. Whatever it is that produced our universe also produced the answer for the ancient mind to think. Without there being a non material aspect to reality, it is very difficult to escape this conclusion. It is part and parcel of the intellectual price tag a materialist is required to pay in order to adhere to their belief. Most are willing to pay this price as it is the price they believe is worth the truth they acquire in return. This truth includes, everything is either determined or probabilistic, therefore free will doesn’t exist and consciousness is just an illusion, an elaborate trick played on us by our brains.