Quite a few things. For a C++ only project, the biggest ones would be reproducibility and speed. But beyond those, I find it saner overall: the language is way easier to understand (~python), and the model of packages, targets, visibility etc makes it easy to organize and manage a large codebase.

The worst part about Bazel for C++ is that it’s not yet as widespread as CMake or plain old Makefiles so it can be harder to get third party libraries into your project, but that’s changing quite fast with the bazel registry, and you have things like rules_cc that help you run other build systems inside bazel.