Clojure is still technically owned by Rich Hickey. Changes to Clojure are ultimately on his time and approval. With that said, both Clojure and Datomic are both worked on daily by Cognitect employees. Nubank in particular has a lot of interest in supporting Datomic development since it is a critical piece in their infrastructure. (Allegedly, Nubank acquired Cognitect because of how important Datomic development is to them). Just because Clojure is slow to make changes to the core language doesn't mean it's not corporate backed. Moreover, Cognitect sells consulting services for Clojure and Datomic, and they sponsor dozens of open source developers. Most notably for this thread, maintainers of Calva (VS Code plugin for Clojure), the maintainer of clojure-lsp, and the maintainer of clj-kondo (static analysis tool used by clojure-lsp).

There's also other consultancies I can think of that make non-trivial efforts to foster a community around the language. Gaiwan has Lambda Island as a subsidiary that publishes video tutorials, hosts the ClojureVerse Q&A forum, and has dozens of open source libraries under the "Lambda Island" organization on GitHub, with active maintenance by Gaiwan employees. Then there's Juxt, which does more consulting than open source, but they have their own open source software (like XTDB) and libraries, which are also maintained by employees of the company. But personally, I think the dozens of individuals that Cognitect sponsors through GitHub is enough evidence for corporate backing of the language, considering who they sponsor end up spanning a vast majority of libraries and tooling that Clojure developers use every day.