LLMs are trained, as others have mentioned, first to just learn the language at all costs. Ingest any and all strings of text generated by humans until you can learn how to generate text in a way that is indistinguishable.
As a happy side effect, this language you've now learned happens to embed quite a few statements of fact and examples of high-quality logical reasoning, but crucially, the language itself isn't a representation of reality or of good reasoning. It isn't meant to be. It's a way to store and communicate arbitrary ideas, which may be wrong or bad or both. Thus, the problem for these researchers now becomes how do we tease out and surface the parts of the model that can produce factually accurate and reasonable statements and dampen everything else?
Animal learning isn't like this. We don't require language at all to represent and reason about reality. We have multimodal sensory experience and direct interaction with the physical world, not just recorded images or writing about the world, from the beginning. Whatever it is humans do, I think we at least innately understand that language isn't truth or reason. It's just a way to encode arbitrary information.
Some way or another, we all grok that there is a hierarchy of evidence or even what evidence is and isn't in the first place. Going into the backyard to find where your dog left the ball or reading a physics textbook is fundamentally a different form of learning than reading the Odyssey or the published manifesto of a mass murderer. We're still "learning" in the sense that our brains now contain more information than they did before, but we know some of these things are representations of reality and some are not. We have access to the world beyond the shadows in the cave.