I think this is happening because there are so many powerful Java libs that are more useful once wrapped in a lispy/clojure-y wrapper, plus the fact the community always seems willing to work together to help people get past the sticky parts, so the whole can be more productive.

I can't comment on the scala community by comparison, but the environment around Clojure simply seems to make people more productive quickly once they are willing to ask questions and read lots of code to learn. Mind getting to that point can be hard.