How does Bazel help reduce build times?

It caches build artifacts in a blob store and just downloads them instead of compiling them where possible

I see, but that's also possible with CMake right? You can use ccache or sccache via -DCMAKE_CXX_COMPILER_LAUNCHER=ccache/sccache.

Sure. If you have any doubts at all that you need Bazel, you don’t need Bazel.

I suppose, but you’d be limited to a small number of supported languages, whereas bazel works for just about anything. Like my sibling commenter noted, you only need it if you really need it.

You are making it sound like it was a compilation process optimization, but it is just CI thing.

Build artifact caching, and also build farm.

In the non-Bazel world, that's ccache and distcc

https://bazel.build/remote/caching

https://github.com/bazelbuild/bazel-buildfarm