Machines had indeed been thought of before, in some cases hundreds of years before.

But before the industrial revolution, such machines, or automata, were just trinkets built to impress the wealthy. Toys. Because this was the best way an inventor could make money out of his machine.

What was needed was a way that an inventor could secure reward for solving industrial problems, securing the title and income from their invention. But not a restriction so tight that it could not be improved by another person.

Developing this nexus of technology, legality and bringing innovators to focus on industrial problems was the key that started the industrial revolution.

Here is a good book on the subject. There i also a British TV documentary, IIRC called 'The Rise of the Machines', which discusses such technology before the industrial revolution, but without really looking at the other issues.