If I had to take a stab in the dark, I would think it has to do with our capacity for problem solving. A better problem solver in the Pleistocene would have better able to meet their own needs and those of their offspring. Better understanding of what's really going on means a better chance of addressing related problems. Just having that tendency meant we would have been more likely to survive. That said, that's speculation on my part, and while I have some anthro in my wheelhouse, I'm no expert on this specific matter. But anthropologists explore this topic every day. It might be worth while to post this question at r/askanthropology to get a more definitive answer.