AFAICT, the only thing this attack relies on, is the lack of scrutiny by developers when adding new dependencies.

Unless this lack of scrutiny is exclusive to JavaScript ecosystem, then this attack could just as well have happened in Rust or Golang.

I don't know Go, but Rust absolutely has the same problem, yes. So does Python. NPM is being discussed here, because it is the topic of the article, but the issue is the ease with which you can pull in unvetted dependencies.

Languages without package managers have a lot more friction to pull in dependencies. You usually rely on the operating system and its package-manager-humans to provide your dependencies; or on primitive OSes like Windows or macOS, you package the dependencies with your application, which involves integrating them into your build and distribution systems. Both of those involve a lot of manual, human effort, which reduces the total number of dependencies (attack points), and makes supply-chain issues like this more likely to be noticed.

The language package managers make it trivial to pull in dozens or hundreds of dependencies, straight from some random source code repository. Your dependencies can add their own dependencies, without you ever knowing. When you have dozens or hundreds of unvetted dependencies, it becomes trivial for an attacker to inject code they control into just one of those dependencies, and then it's game over for every project that includes that one dependency anywhere in their chain.

It's not impossible to do that in the OS-provided or self-managed dependency scenario, but it's much more difficult and will have a much narrower impact.

That, and the ability to push an update without human interaction.

JavaScript does have some pretty insane dependency trees. Most other languages don’t have anywhere near that level of nestedness.