Many, many parts of the standard library are written in C. Most performance critical parts are.
Do you need a pre-compiled tomllib? If you are using toml a lot, maybe. But chances are that you aren't reading a lot of toml files, and if you are, then you're probably already using rtoml.
Hmmm. Interesting. Why not a project that just simply writes the (Python parts of the) standard library in C directly?
Many, many parts of the standard library are written in C. Most performance critical parts are.
Do you need a pre-compiled tomllib? If you are using toml a lot, maybe. But chances are that you aren't reading a lot of toml files, and if you are, then you're probably already using rtoml.
The json is also still Python code. ujson helps but still json.dumps is suuuper slow.