They could not. The reason is that the “market” is made up of all participants and information would flow more easily. The other side of the manipulation would use their “not poor” intelligence and find an optimum way to fleece the unknowing.
Remember, wall street’s lesson: a man with a lot of wisdom meets a man with a lot of money. After a period of time together the man with a lot of wisdom still has the wisdom but a lot more money and the man with a lot of money, has a lot less of it, but a lot more wisdom.