I think Peter put it will. You may not have spent too much time, but you did basic on-site
SEO. And although the SEs may be savy, they still like well structured sites. If you have a well structured site, quality natural content, and links, you'll do well. Structure and Content are on-site
SEO. It doesn't take much more effort to properly structure header tags, images, etc.
A lot may have to do with how competitive the term is, as well.
Also, I'm sure others will point out that on-site
SEO includes making sure your site is accesible to everyone. Although, I will have to admit, we haven't gone that far.