I think a far better approach to memory safety in C projects is to evolve tools and annotate existing code.

The advantage of Rust is that it already exists. Someone has to do the work to bring that to fruition before it's practically applicable.

these changes driven by enthusiastic and opinionated small group

In this case, that group includes Linus.

Going into existing projects and changing them according to "opinions" is a really bad idea.

The Rust for Linux folks already worked on Linux for years. They aren't outsiders.