Why are people so stupid?

My freinds are so fucking stupid, they believe everything that comes out of (let's call him... Kane) Kane's lying mouth he literally has everyone but 2 of my freinds in that group in his grip, me and another of my freinds have literally talked about how much we hate the little cunt, and he makes some of the most obvious lies "I used to be a pirate in one of my past lies" "I don't talk about the past life where I got mo**sted" that got me especially angry because we have a couple people in that group who have been mo**sted, he also blames everything bad he does on his mental health, or not taking him medication, seriously? I have mental issues too. But everyone I make a mistake I own up to it and say sorry, seriously, he needs to stop being such a little lying asshole, and own up to the stuff his done