She wrote up a set of safety guidelines for the beef industry and McDonald's adopted her recommendations. You couldn't sell beef to McDonald's without following her guideline.
McDonald's buys so much beef, this became the de facto industry standard.
You can't put a gun to someone's head and force them to love you. You can't get blood from a turnip. And draconian measures generally fail to get real results.
Carrots and stick sometimes work. But "the beatings shall continue until morale improves" is generally counterproductive. It doesn't supply the necessary competence for setting a higher standard and usually actively disincentivizes trying to solve the problem.