Well I think confirmation bias is part of it. Also affinity bias. Spreading of alternatives. So is the need to belong to a group, which is stronger in some people than others.

I am not sure everyone knows the weaknesses if their belief system. If you come from an authoritarian background, you are taught from a young age not to question authority and are punished if you do.

I do think some people are highly aware and exploit people. Others may not understand the underlying mechanisms, but they can smell it a mile away and use it to their advantage.