The brain prepares the answer before it actually does it in action. The experiment has shown that before we “freely” decide to do something, the brain already decides those 7 seconds before. Free will is an illusion here because, the brain is already deciding the action and we are merely the medium who is carrying out the action. It also means that are following the orders of the brain. I think the idea of free will is “illusion” is true. This is actually the way brain works.