Those who participate in risky sports often do so to confront their fears.
Conclusion (so)
Confronting your fears probably increases your self-confidence.
Evidence
People who participate in risky sports often do so to confront their fears. Rock climbers are more likely than others to have once suffered from a fear of heights.
People who participate in risky sports also have more self-confidence than others.
Evaluate
The author is concluding a causal connection (X increases Y) between two things (confronting fear / higher self-confidence) based on the fact that both of those things are correlated with people who do risky sports.
The author's conclusion is trying to offer an explanation a curious comparison between risk-takers and the rest of the population, when it comes to self-confidence.
Curious Fact ... Why is it that people who do risky sports tend to have higher than average self-confidence?
Author's Explanation ... It's because they participate in risky sports to confront their fears, and confronting your fears increases your self-confidence.
Goal
As always, we can weaken an Explain Curious Fact argument two different ways:
(more common) 1. Suggest an Alternate Explanation for why people who do risky sports have higher than average self-confidence.
2. Hurt the plausibility of the Author's Explanation that people engage in a risky sport, in doing so confront their fears, and in doing so increase their self-confidence.
We know that the two classic Alternate Explanations are Reverse Causality and 3rd Factor, .