I think I'm a little smart, but not too much higher-than-average. But because I constantly need to think about everything, I'm always exercising my brain, and working on problems that everyone else ignores half their day. I've known plenty of people way smarter than me that didn't achieve as much, because they just wanted to turn off and tune out. Drink some beer. Watch some mindless movies.
I'm going 24x7. So like the multi-billionaire CEO who's only in that position because he works 80hr/wk and never turns it off... I'm doing well in tech (and my hobbies!) because I just can't stop thinking about algorithms and solving problems. My hobbies and entertainment end up being highly-technical intensive thought-requiring activities.
Curiosity is also a trait I've got, but I suspect it's just a result of the high need for cognition. I find that I'm not that curious about things that don't make me think a lot.