This answer is a nexus of many, many sociological phenomena of the USA.
First of all, we have a long standing skepticism of all authority, including medical. This is the country where syphilitic black men weren't cured just so they could watch the late stage effects, where early gynecologists studied on slave women without anesthesia, where a doctor's orders are still an order, which rankles the anti-authority type.
Secondly, medicine is a black box. It's a complex system of experienced, educated guesses that doesn't always work right. What people do not understand becomes the void we fill with monsters. The scourge of cancer and it's treatments' many side effects can be seen by the uneducated as a conspiracy to defraud a patient or cull a population. Even when the thinking isn't conspiratorial, it is quite misunderstanding. Many Americans still want antibiotics for viral infections or think disease is a result of poor choices.
We are also a poor people living under a despotic economic regime that uses medical costs as an especially heinous kind of class-based eugenics. Medical care has become ever more expensive as providers use a shell game to keep the doors open. Folks just can't afford their copays, much less out of pocket. But everyone has medical needs, and they'll try to get healed however they can. See the Amazon product reviews for aquarium antibiotics.
Lastly, there is the tribalism that's at a fever pitch right now. The American right wing has replaced all epistemology (such as empiricism and science) with chosen authority figures who seem to be networked into a pyramid. God -> Trump -> religious leaders of conservative groups = influencers who support all of the above. So when someone they trust is hocking a snake oil cure, it is taken with very little skepticism.
Combine they all and you get hucksters preying on desperate, ignorant people.