Maybe to appeal to C and C++ developers. Rust makes its syntax superficially similar to C/C++ syntax in many other ways: pointer/reference syntax, declaration of "struct" types, generic types using <T>, curly brace block structure, and the naming conventions enforced by their lints. To be fair, many of these traits of C and C++ are also copied by other programming languages (e.g. curly braces). But they could have gone in a different direction and had pointer and record syntax more like Pascal, or made a syntax more like OCaml, Standard ML, or Haskell.

I think it might be due to the O'Caml influence on early Rust. They call them enums there[0].

[0] https://www.ocamlwiki.com/index.php?title=Enums_in_OCaml

My best guess is Java.

Edit: I guess if you've never seen that this is, uh, controversial. Or something. Anyway, Java enums are full-strength classes, look at the planet example here https://docs.oracle.com/javase/tutorial/java/javaOO/enum.htm...

This is more like a Rust enum than a C one, I think you'll find.

Typescript has actual enums. They behave just like Go's (for better or worse).

It's not clear why Rust got confused.