Answer:
The most direct cause of the development of factories in Manchester (the first industrial city in the world), was the invention of the spinning jenny by James Hargreaves, and the invention of the water frame by Richard Arkwright.
These two inventions made the production of cloth from cotton a lot of faster and easier. Shortly after, these two inventors founded factories in Manchester, and hired people from the countryside.
From this moment on, the industry boomed, and Manchester became the first industrial city in the world, effectively starting the Industrial Revolution.
