Once someone becomes convinced of something it is often very difficult to change their mind despite logic and even strong evidence. I have noticed this even in my own thinking despite being aware of it.

You become invested in an idea by your own thoughts and actions as well as statements to others. Then to change your mind you have to admit to yourself that you are wrong as well as to others who may still hold the mistaken belief. This can be unpleasant so many people just avoid it.

Keep in mind that very few things are black and white so there is always some "reasoning" that can defend the incorrect belief even if it is very unlikely. And there are often people who benefit from the incorrect beliefs (you may disagree but I think the $5 billion US vitamin/supplement industry is a good example).

While if everyone had excellent "critical thinking" tools it should help I'm skeptical this would overcome natural human biases such as pride. And perhaps it is a good thing that at least a few people disagree with any consensus no matter how strongly supported by logic and evidence.