One dynamic is social trust. We tend to believe those in our social circle. Within this circle, ideas can be contagious, spreading from person to person without being questioned. Not only do we trust what we are told, we learn vicariously from the personal experiences our friends tell us about. We also trust some forms of evidence more than others. For example, people may believe shared beliefs even when they are not confirmed by a preponderance of scientific evidence. Another major contributor is conformity, "a preference to act in the same way as others in one's community"(p. 60). Even when presented with facts contradicting a group's stance, its members may ignore them because it is more important to fit in.
However, social trust and conformity are not the only contributors to our gullibility. We can be the targets of well developed misinformation campaigns designed by special interest groups. Such groups purposely manipulate what we are told. They may select only only the scientific evidence supporting their interests, even though most scientific evidence supports the contrary. Exploiting our social trust and need for conformity, they may have a trusted, high status person in the community echo their position. There are increasingly sophisticated methods of cyber-falsification through social media conduits.
The above contributors to our acceptance of false information interfere with our ability to make realistically informed decisions. In my opinion, a good dose of suspicion is a necessary protection, as well as an open-mindedness regarding other possibilities. Civil discourse and personal research are other important contributors to reduce the impact of false information.
O'Conner, C., & Weatherall, J. O. Why we trust lies. Scientific American (Special Issue), 2019, 321(3), 54-61.