because it thought it was cool
"Theft" is not a challenge for an inventor any more than it is for anyone else. Theft is taking something with the intention of permanently depriving its owner of it. Copying an invention is not theft because the inventor has not been deprived of the invention after it has been copied: the inventor still knows what the invention is. On the other hand, the risk of someone copying his or her invention is a challenge for an inventor. The person who copied the invention can get the benefit of the invention without any of the cost and effort that the inventor had to go to to make the invention. That might make the inventor worse off. The patent system exists to allow inventors to protect their inventions.
They need to obtain a patent on their invention.
an invention
The inventor invented an invention.
There is no one inventor, and no one set amount they can make. Many make nothing, a very few can make millions. Depends on the invention, and how much of a market there is for that thing.
Fire is not an invention.
"This Invention" - what invention? You don't mention one.
You first patent it, but check out how that works in your country because it differs.
YES
yes
He was not an inventor.
Such a person is an inventor.