Clojure is functional(valuable for correctness), based on lisp(a proven language), compatible with the JVM ecosystem, and attracts high quality programmers. Janestreet uses Ocaml for similar reasons.
I'm less familiar with Diatomic, but a quick look around seems to suggest that companies like Facebook and Netflix are paying customers, and Nubank are the owners. Plus it's written in Clojure. If it works well for them, seems like it's probably a fine investment.
Flutter might get canned, but also Flutter apps are cheap and high quality. It was probably a good choice, and can easily be replaced if the project dies.