Repetition of a lie, repeated over and over, and especially during moments of high emotion will convince people that it is true. It is a form of brainwashing (if you're gaslighting a victim) or a form of image or narrative management (if you're trying to convince someone else).

I was going through comments I've said, and read this comment (adapted) from u/PharmDeezNuts_:

What [they] have realized is that they can make up lies over and over again and then call anyone that corrects them biased. Passive observers who don’t necessarily know the truth or follow the claim will come to that conclusion over time.

and started thinking of it in context of the con artist material.