It's not just killer JVM interop, it's killer all around interop. Clojure relies on interop more than any other major language, the language has inherent syntax around it and even its standard library is designed with it in mind. That makes it very easy to adapt over different runtimes, giving Clojure more reach than most. That's why you have Clojure JVM, Clojure CLR, Clojure Unity, ClojureScript, Clojerl (Clojure on BEAM), etc.