I’d say that Clojure simply wouldn’t exist at all if it wasn’t for Rich Hickey, and at this point, it’s rock solid and stable and could be used as-is for decades maybe even if he stopped being involved.
Clojure’s development has been very measured – very conservative – unlike many other languages, to the point that code written a decade ago for Clojure 1.3 (or earlier) still runs unchanged in nearly all cases. That careful approach also means that prerelease builds are stable enough to run in production: we first went to production with an alpha build of 1.3 and we’ve run prerelease builds of every version of Clojure since then in production too (we’re running 1.10.2-alpha4 in production for most of our processes right now, with at least one process already on 1.10.2-rc1).
It’s also worth taking a look at the list of folks who have signed the contributor’s agreement – https://clojure.org/dev/contributors – and many of those have actively contributed to either Clojure itself or one of the many Contrib libraries that are managed under the same process (I can’t find the specific list of people who’ve contributed to Clojure core but even that subset of contributors is pretty long).
Clojure generally appeals to more senior developers who have experienced the pain points of other languages and other styles of programming and are quietly looking for “something better”, that enables them to do their job more productively and more effectively and so they mostly just go about their work without fanfare. Surveys have repeatedly shown that Clojure developers report themselves as the happiest, on average, of all developers (and that salaries tend to be higher, on average, too but that is most likely tied to Clojure developers being more senior on average).
A language doesn’t need to be popular to be successful – and popularity is a non-goal for Clojure.