I'd have expected much more to be in C#.
As note, Midori did power part of Bing during its existence.
And Microsoft security is now advising to move new development into a mix of C#, Rust and constrained C++ (Core Guidelines).
Check DoD security assement of Multics versus UNIX regarding ease of security exploits, and how using PL/I prevented the large majority of them. On the mobile now, the document is accessible at the Multics history site.
Or any deployment of High Integrity Computing OSes for that matter.
https://kennykerr.ca/2019/01/25/the-state-of-cpp-on-windows/