This explains your cousin.

https://www.vox.com/science-and-health/2018/4/20/17109764/deepfake-ai-false-memory-psychology

«Here’s one possible reason these redditors believed in the movie so intensely: the Reddit forum itself. Social media brought together like-minded people. “Any type of corroboration is going to strengthen your memory for something, whether it’s true or not, and your confidence in your memory,” Frenda says. These Shazaam  truthers were all riffing off one another, giving each other subtle suggestions to form a false narrative that exists in their minds.»