And while this was necessary to Rust's success, I don't think it was sufficient, insofar as it also needed a good deal of corporate backing, a great and welcoming community, and luck to be at the right place at the right time.

Haskell never tried to be more than a academic language targeting researchers. OCaml never had a big community or corporate backing. Scala never really had a niche; the most salient reason to use it is if you're already in the Java ecosystem and you want to write functional code. The value propositions for each are very different, so these language didn't receive the same reaction as Rust despite offering similar features.