People are stupid; given proper motivation, almost anyone will believe
almost anything. Because people are stupid, they will believe a lie
because they want to believe it's true, or because they are afraid it
might be true.

People’s heads are full of knowledge, facts, and beliefs, and most of it
is false, yet they think it all true. People are stupid; they can only
rarely tell the difference between a lie and the truth.

— The Wizard's First Rule