Milling with water power produced surplus flour. That gave the mill more to trade for other things, however, eventually other mills sought the same benefits, and with society only needing so much flour milled, eventually there was a surplus, and it drove the competition through the roof. The early benefit went to the innovator, the late benefit went to society having cheap access to flour and milling services.
This is the trend of everything. When an industry becomes a commodity, it’s time to find another innovation.