GPTs are language models, not "fact and truth" models. They don't even know what facts are, they just know that "if I use this word in this place, it won't sound unusual". They get rewarded for saying things that users find compelling, not necessarily what's true (and again, they have no reference to ground truth).

LLMs are like car salesmen. They learn to say things they think you want to hear in order to buy a car (upvote a response). Sometimes that's useful and truthful information, other times it isn't. (In LLMs' defense, car salesmen lie more intentionally.)