D and Ada both use a GC in many contexts, and are not half as interesting in their GC-less contexts. They both initially only had a proprietary compiler, which durably harmed adoption. They both seem to cater to fewer domains than C/C++/Rust. Today Ada is only used in high-stakes industry, and D doesn't seem to have any claim to fame. It's a pity that neither succeeded in their time, but there's no good reason to use either of them today.

Zig is very promissing, but is just too new.

You failed to mention C++. It's well loved (and hated), has many pros and cons compared to C, and is used for kernel development (just not Linux).

It's silly to think that the only explanation for Rust success is community lobbying. Rust has many concrete advantages, like being safer than C/C++/D/Zig, being fully GC-free and suitable for kernel and embedded development, having actually gained significant traction, having great tooling/docs/ecosystem... And generally being a language that people enjoy. Rust isn't the end-game of kernel programming, but it isn't just "yet another better C".