Rich Hickey's previous projects to clojure were all about Lisp<->JVM interop (see http://foil.sourceforge.net/, but there is at least one other) -- so I think he found limitations to what you can do.

>But the thing is, Armed Bear Common Lisp (ABCL) already offers JVM interop.

Yes, a half-arsed, barely supported interop. And slow to top.

>If someone sat down and really massaged it, the currently clunky interop there could be just as shiny as Clojure.

I rest my case.