There’s a disconnect in the brain, when visible evidence shows one thing but you’re repeatedly bombarded with people from all sides telling you that your eyes were deceiving you. Your brain tells you that all of those people can’t possibly be lying to you at the same time, about the same thing, and so you begin to believe the lie. Then they’ll throw in a tiny bit of truth mixed in with all the lies, and your brain will latch onto that tiny bit of truth in order to soothe itself and say, “See? They weren’t lying to me… so that other thing I thought they were lying about… must have been my misunderstanding.”
And now you’ve swallowed the hook and sinker, getting ready to be strangled by the line.