Carbon exists so that it's possible to migrate a large C++ code base, like Chrome, from C++ to something saner, incrementally.

The most important attribute of Carbon is not the specifics of the syntax but the fact that it's designed to be used in a mixed C++ / Carbon code base and comes with tooling to convert as much of C++ as possible to Carbon.

That's what makes Carbon different from any other language: D, Zig, Nim, Rust etc.

It's not possible to port a millions line C++ code base, like Chrome, to another language so large C++ projects are stuck with objectively pretty bad language and are forced to continue to use C++ even though a better language might exist.

That's why Carbon is designed for incremental adoption in large C++ projects: you can add Carbon code to existing C++ code and incrementally port C++ over to Carbon until only Carbon code exists.

Still a very large investment but at least possible and not dissimilar to refactoring to adopt newer C++ features like e.g. replacing use of std::string with std::string_view.

That's why it's a rational project for Google. Even though it's a large investment, it might pay off if they can write new software in Carbon instead of C++ and refactor old code into Carbon.

Maybe it could be useful alongside HTMX even: client-side HTML manipulation for simple things and server-side HTML hydration and rendering for complex things.