I'm unconvinced that metal smiths of the iron/steel age did not "understand how it worked." That certain smiths and geographic regions produced consistently high grades of steel suggests they did have an understanding, albeit it an understanding grounded in a world model that differs substantially from our own modern framework. If, for example, an alchemical world view sufficed to describe and predict the results of forging a particular metal or alloy then it was sufficient for understanding within the constraints of what was needed. Plenty of modern bladesmiths have no deeper understanding of metallurgy than "this is good for X, this other is not according to experts or experience."

Aristotelian physics was sufficient in the time and geographic area in which he operated (friction as primary) but was insufficient in a larger domain compared to Newtonian physics (force has primacy). Both served to bring us to and through the industrial age, but then the domain expanded and quantum physics was needed.

Don't discount the genius of our ancestors regardless of archeological age. We may feel smugly superior playing with our tools of the silicon age but get magically transported to the stone age naked and with no access to external knowledge and try and achieve in the basics of food, clothing, and shelter... let alone tools such as hand axes, skinning knives, arrow and spear points, etc.