Conspiracy theories are a slippery slope. You might not believe something at first, but they are peppered with enough truth that you begin to accept them all because one part was right. "Question everything," as they often tell you. The problem is, facts and science usually comes from people in authority - the people you're told to question. So you begin blanket distrust all "authority". Which ends up being anyone telling your something with authority. Government, science, medicine, police, Greta...
I'll happily question - but the problem comes when your bias won't let you trust anyone or anything. In fact you deliberately take the opposite stance because "they lie" and they're probably "out to get" you. Then it really is dangerous - and you feel clever, because it's like knowing some secret knowledge the rest of the world doesn't - because the "sheeple" believe the spoon fed lies.