> Markets are the sum of the information everyone has about prices (even if that's not evenly distributed), and if you could co-ordinate to rig that, you could rig literally anything.
The market being rigged (in the casual sense used here) does not require anyone to be manipulating all of the factors that affect prices; you just need to be able to cheat on some input to the system. Trading on non-public information may not always be a successful strategy because you might get unlucky and some other factors could unpredictably outweigh the impact of the insider information you're basing your trades on—but on average, insider trading works until/unless you are caught and prosecuted.
The market being rigged (in the casual sense used here) does not require anyone to be manipulating all of the factors that affect prices; you just need to be able to cheat on some input to the system. Trading on non-public information may not always be a successful strategy because you might get unlucky and some other factors could unpredictably outweigh the impact of the insider information you're basing your trades on—but on average, insider trading works until/unless you are caught and prosecuted.