Why wouldn't WP rank well? There is nothing saying WP-sites can't rank well. However, looking at the code, I'm guessing they HAVE WP somewhere in there, perhaps pushing specific blog-style content, or something like that, either in a subdomain or subdirectory - the code for the main page doesn't look like WP, unless they've gone ahead and modified the base-files, which of course they might've, although that would be a disaster when it comes to maintaining the site.