It isn’t a matter of some people being gullible and others aren’t, everyone is gullible in this sense but a lot depends on prior experience, knowledge, peer groups and a lot of other factors. Trolls and conmen play a big part in building a cohesive narrative for fun and profit. People who are looking for a community gravitate to things like this and are easily influenced due to their lack of a counter balancing force in their lives (friends, community, work, faith, etc.). It becomes the thing they live for, part of the story of their life and a framework they use to understand the world. The scary thing is a lot of the world works this way and only varies in quality and pervasiveness. It’s the air we breath so it’s hard to get perspective on. How can you know for sure that something is true if it is beyond your means to verify? You have to appeal to authority or the majority. We do this with practically everything in our lives out of necessity, it’s impossible to vet everything. Most of it is valid and based on widely distributed independent verification. But there are messy areas where either this isn’t possible or where there is strong motivation to argue for a particular view. Politics and religion are pervaded by unverifiable claims and opinions. But it reaches into every aspect of life where there is uncertainty, money or an axe to grind.