Guess Rust is more built for memory safety not concurrency? Erlang maybe? Why can't we just have a language that is memory safe and built for concurrency? Like Ocaml and Erlang combine?

Are you looking for Gleam? Simple but powerful typed functional language for BEAM and JavaScript. It’s a bit high level compared to Ocaml in terms of needing a thick runtime and being somewhat far from machine code.

Really beautiful language design imo. Does a great job avoiding the typelevel brainfuck problem I have with Haskell.

https://gleam.run/

Rust is absolutely built for concurrency, even moreso than for memory safety--it just so happens that memory safety is a prerequisite for thread safety. You're going to have a hard time finding any other industrial-strength language that statically prevents data races. If you can use Erlang, then sure, use Erlang. But if you can't use Erlang, and you need concurrency, you're not going to find a better candidate than Rust.