Overconfidence is a survival trait. If he survives well through his self-professed capabilities, then he's succeeded.
I feel this is false for two reasons. In a pure survival situation, overconfidence does not necessarily lead to survival. Over estimating yourself could often lead to situations where you can not survive. For instance, "can I kill and eat this sabertooth tiger?" No, the risk is not worth the reward, overconfidence would kill you. There are sexual selection situations I can see it being a positive, but overall it is worse then having the correct amount of confidence.
Second, we are not in a survival situation. The only survival we worry about is social and professional survival. Having high confidence is obviously important, but it must be within range of your actual skill. In this case, Dickie's confidence is through the roof, but his actual skill does not match. What I'm saying is that being confident in your skills is ancillary to your actual skills, and if it differs too much you risk being mocked and disliked (as I have demonstrated

).
Maybe I'm reading too much into your post, but I think where we really disagree is that you think success is personally subjective, and I think it is collectively objective (not based on your opinion of yourself, but determined collectively).