The study tested the actual knowledge of people on these subjects. They found that people who disagreed with the scientific consensus knew less about these subj

The study tested the actual knowledge of people on these subjects. They found that people who disagreed with the scientific consensus knew less about these subjects than people who agreed with the consensus, but overestimated their confidence in their knowledge of the facts. So in other words those who agreed with the consensus were better informed and had a more accurate assessment of their level of knowledge.