My theory

It coalesced at a time when science was becoming more accessible to the masses, more educated technicians running around engaging in work and trade.

And these technicians were frustrated by bosses who didn't understand the science and technique behind things.

So there was great inefficiency because the bosses hadn't caught up to the technicians in their understanding of the world.

And so the political idea of "put in charge the people who actually understand the problem" caught hold of the technicians, and they were fired up for a period of time and they called it technocracy.