Perhaps ... "rv menu" appears to perform well because those looking for food menus for when they are off in their RV are interested in just _looking_ at RVs? Did they mainly click the expensive ones? [That's what I'd do, like "ooh, fancy; I'd like one of those"]

Interest, indeed clicks, don't mean revenue will follow unless they were actual sales actions.

Now, it could also be that you can sell RV hire to people researching for an RV trip using "RV menu" ...