[emporas]

> It seems like the high ancient world was so close to industrializing.

There are many factors at play. Serious industrialization requires several components to build on. There is a reason for example that "All roads lead to Rome". That's because no roads lead to Athens.

The machines to do the work, were the animals. Horses to carry merchandise around, bulls to plow land were used all over the place, by Romans, Greeks, Sumerians, Persians, everyone.

Metal constructions used for heavy work like iron, were too brittle, and bronze was too weak to withstand significant forces. It is only the last two hundred years that strong alloys were developed for industrial applications.