> weird idea that intelligence without effort can yield results
In my experience, that 'weird idea' comes from early schooling. Highly intelligent (gifted?) kids generally don't have to exhibit any effort on school work, at least up to a certain time. I can tell you that, in my case, I coasted up until around 11th grade, then I hit a bit of a mental wall. I'm sure other physiological changes impacted, but at core, I didn't know how to study or exert effort in 'learning' - everything had just fallen in to place for so long that I didn't have the skill or experience to learn how to get better. This was a confounding factor in college as well.
I've shared this with other folks, and had more than a few people share similar experiences.
If Usain just ran really fast, and people said "wow, you're fast", but he wasn't trained at how to get better, he probably wouldn't have become a world champ. But with 'raw intelligence', that often doesn't receive the same sort of coaching and support as specific sports or other identifiable talents.