Scala, OCaml, and Haskell all approach programming from a functional-first perspective. What no other language did before Rust was to bring those features to such a well-designed imperative core.

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.

> There were lots of languages giving you just that, and they never had this amount of hype. See Scala, OCaml, Haskell, etc.

They weren't hyped because they didn't have a silly party trick like microbenchmark performance. But they give you all the practical benefits of Rust and more.