This link answers your questions about companies using Clojure.

https://clojure.org/news/2021/04/06/state-of-clojure-2021

(700 Clojure devs at the biggest shop, Nubank.) Although I would be surprised if their salaries were at the top of global developers.

Especially considering Nubank is Brazilian, and even though they pay well for Brazil I doubt it gets close to US standards

~3k to ~5k dollars a month, no vesting, and I'm not sure if there's a bonus structure. At least 22% of the Clojure workfoce make entry-level money by US standards, so the other 78% must be doing pretty good

Geographic distribution of developers and relatively low amount of devs? If most Clojure devs are in the US (where generally the highest dev salaries are), whereas for other languages they are more spread out around the world, then Clojure will be at the top even if it isn't necessarily the top paying programming language in the US itself (no idea about that).

Fewer companies use Clojure, while Clojure attracts talented, experienced programmers. This community of Clojure developers paired with few opportunities creates higher demand and thus higher pay

Walmart has a decent amount of Clojure

https://clojure.org/community/success_stories