Marx on Capital as a real god

What about the individual people who participate in this social practice? Surely their individual consciousness, their ideas, and their behaviour matter, and make a difference?

To a certain extent they do of course. But individuals come and go, but capitals live much longer than any individual human. The people controlled by the capital — that is the workers that supply labour to firms, and capitalists that exploit them and extract profits — are mere replaceable components in the control loop, mechanically performing prescribed functional roles.