The youth of the language should be a reasonable predictor of that difference, alone.

It may indeed turn out that the way Rust's learning curve is front-loaded will prevent it from breaking into the mainstream, but that's a separate issue from developers deciding it's unsuitable for work after they learn it.

With the exception of swift - which has the distinct advantage of being one of two languages you can write programs in for the most popular (? probably true since Android's market share is scattered across many models) piece of consumer hardware in the world - I can't think of a language of similar age to or younger than rust with as many job ads.

You see plenty for C/C++ because they've existed forever, have a huge amount of code written in them, and a huge number of programmers who already know them. Just like with Cobal you will almost certainly see plenty for C/C++ many years into the future. That doesn't really say much about Rust.