For me, management and leadership are two very different skillsets. Sometimes they vest in the same person; but usually I wouldn't expect managers to be deep in code; just like I wouldn't expect team leads to be trying to write project plans and delivery schedules.
Having worked in/with the automotive industry for a long time, I'm saddened, but not surprised, by this. The big problem is that most 'cybersecurity' experts in automotive are not actually well versed in modern software engineering.
It is structurally possible yes; libraries are generally composed of multiple compilation units. What you would need to do is to construct the .o files from your C, and then get cargo to add them to the linking for your rust crate. I think that'd be the easiest approach.
currently for me, it's about having good examples and docs easy to find. I'd love to replace my pile of ansibled debian systems with nixos but centralised management of multiple systems isn't well documented. At least not that I've found for myself.