The languages are as different as Python and C++, I honestly don't really see a Rust vs Dart story. Note that Rust is approved for use within much of the source tree, but outside it is only not supported. Johnny end-developer, whoever that is, could still use Rust if he insisted, coding against C bindings.
If Johnny doesn't like JVM languages, or C++, all they get is a bare bones C API, which requires JNI even for opening files, asking for permissions and so forth.
I don't know what "conspiracy" you might be referring to. There's a natural tendency for organizations to gravitate toward tools, such as programming languages, that originated there. That's just human nature, though, not anything nefarious.