In my experience, curiosity and intelligence are very strongly correlated. There is a real gap between people with the curiosity and ability to explore and learn, and people without. This is often handwaved as "motivation" but it's more than just that.
In fact, the gap is so large that it can be really hard for a person on one side of it to understand how people on the other side think.
I think part of it is that geniuses gets (or at least feels) rewarded whenever they try learning, while other people might not. For the same amount of effort, the amount of new knowledge gained by other people is fewer than what geniuses can get. Overtime, leaning no longer feels worth it. Thus normal people no longer feels curious while geniuses still do.