As you wrote, even an apparently simple idea like currency is actually incredibly complicated in its historical reality, so complicated that there are thousands

As you wrote, even an apparently simple idea like currency is actually incredibly complicated in its historical reality, so complicated that there are thousands of books about it, very active research, and competing school of thoughts that propose completely different and incompatible theories about what are the "causes" and what are the "effects". So, my opinion is that every simple explanation of any big phenomena regarding human history actually explains very little.