The Polstar software is written in Rust?
There's usually a mix of Assembly, Simulink, C, C++, Java, JavaScript, Shell scripts, Python, etc...
I've seen the OS be various flavors of embedded Linux, QNX, or even Ubuntu.
You can usually find a bit of everything even in a single vehicle. The code is integrated by an OEM and can come from dozens of potential suppliers.
More seriously, most ebike firmware is written in C.
That's off the point though. The choice of language matters, but it matters less than the development process and the professionalism of people involved.