It seems like when I run into this same scenario, I'm dealing with a mature URL that has simply positioned itself in a market and been able to hold. It's not that they are technically doing things "right", but apparently are not doing enough wrong to affect the gravity of their age and backlinks.
I think the original registration on that domain was 2003. Are there any other sites ranking around some of your key phrases that are less than 1-2 yrs registered? Age could be a factor.