Yes, conspiracy theories can be dangerous but, unfortunately, a certain percentage of the human population appears to be hard wired so as to be susceptible to such beliefs. Also, whether or not someone is susceptible doesn’t necessarily correlate with their intelligence.
Put another way, we’ll probably always be stuck with a good percentage of our population buying into ridiculous, unprovable beliefs no matter what. It one of the downsides of having a Democracy which, in the words of Churchill “…is the worst possible form of government, with the exception of all other forms.”