It seems counterintuitive, but it explains a lot. A new mathematical model explains the spread of useless quackery not becuase it seems to work, but in fact because it is useless.
In short, people emulate each other. If you see me taking a medicine for an illness, you are likely to try the same remedy. The longer I stay sick, the more people I will meet, and the more people will see me taking the treatment. If I am cured quickly, I may only pass along the effective treatment to one or two people. If I am not cured, I may pass along the ineffective treatment to dozens.
The study says that this is not always the case, though it nevertheless goes a long way to explaining the widespread belief in useless folk remedies.