Sure that index isn't great (I think it's basically a regurgitation of Google Trends), but I don't think you're suggesting Clojure is actually a popular language are you? Which is the only point I'm trying to make (that it isn't popular).

Clojure is reasonably popular as far as programming languages go. It's not difficult to get a job as a Clojure developer, particularly in certain sectors (fintech and healthcare are the heaviest Clojure users). Of course C++, Java, C# and PHP dwarf both Clojure and Rust by several orders of magnitude.