They believed these Sacred Symbols could animate and act, that images on their walls of the King and others could animate and act, like in a movie, to protect them from their enemies. There had to be some basis for that belief to continue for so many thousands of years. Perhaps because they saw it happen?

In Sun Child, Prince of Egypt, and the Series: Tales of King Tut, those mysteries are explored.

I have also posted on our blog some excerpts and explanations of what Magic was to the Ancient Egyptians, at least what some scholars have learned so far.
See: Wallis Budge's take on Egyptian Magic; and the Nine Measures of Magic from Sacred Texts.