The point is that the brain operates on information, not things. The thing you think is the external world, that's just electricity flowing through your neurons. When you see a dog, that isn't a thing in the world, but a signal in your brain. In principle we can take a knife and cut that connection at any point and replace the real signal with an electronic box that gives the same signal.

You don't need a body, you need electrical signals your brain interprets as body. And in principle you don't even need a brain, you could replace that with some matrix multiplication or transistors that do the same stuff.

The important part of consciousness is being able to figure out what of the sensory input is correlated to your own action and which was caused by the rest of the world.