I don't think there's anything remarkable about this website that could be considered a "big win" for Lisp. It's a totally run-of-the-mill dynamic web app that could have been developed more quickly in any web framework such as Rails or Django.

In fact, the hacky way it was implemented in Lisp had some clear downsides. In the early days (I'm probably going to mess up the details but hopefully the gist will come through) there was a notorious failure mode due to the way entities such as stories and comments were stored in memory using closures. These closures obviously had to be cleaned out periodically, and so if you stayed on a page too long and then clicked a link on the page, it would be invalid. You'd have to go back and refresh the page and click the link again. I don't think it's out of bounds to say this website is basically a rehash of the hacks pg came up with in the mid 90s to implement web apps in Lisp for Viaweb. The fact that he got rich off those hacks may have been a selling point for Lisp 20 years ago when he wrote Beating the Averages, but the world has moved on.