Conspiracy theorists (important: multiple) often have one or more of the following attributes which is why you see a wide range of intelligence in the group.
1. People with mental illness.
2. People with low intelligence who are unable/don't understand logic, the scientific method, and concepts like ecree, They are easily fooled by others. They may also have a bias like hating or mistrusting the government.
3. People who are insecure. Being a conspiracy theorist makes you feel smarter than other people as you are part of a select group of who know the truth. The masses are stupid or as they say now "asleep" but you've figured it all out via Google.
This is why much of their talk is less about how they can prove their claims and more about the people who don't believe. They refer to them as "sheep" or "not awake. The focus for them is that they are right which may help with their insecurities.
4. People who don't feel they have a purpose in life and are looking for a meaning. Want to be a part of a group that is bound by something important and there's almost no effort to join? Bam, now your job is to get that information out there and covert the masses, a goal that will never be finished and thankfully take up your entire life.
5. People who were originally lured in because of the other reasons and no longer believe. Because they made it their life, maybe spent excess money, wrote books or made absolute claims they don't want to look stupid so they never admit their change. This is especially an issue on the internet where the whole world can fest on your failure.