[ohgodplsno]

Another, less kind answer: it was the flavor of the month about a dozen years ago, some devs decided to build everything in Clojure, now the software that runs entire large companies is in Clojure, nobody knows how to maintain it, so the only ones left over take large salaries. It's kind of like COBOL in banks, except it was hype driven and not we-had-no-other-option-at-the-time driven.