Go, although with it's GC it's debatable to what extent it's suitable for very low level software. And honestly the language choice was only the tip of the ice

Go, although with it's GC it's debatable to what extent it's suitable for very low level software. And honestly the language choice was only the tip of the iceberg, it took years of people adapting before systemd became usable. And it still doesn't handle circular dependencies better than arbitrarily which is ridiculous, literally one of it's main jobs is to handle dependencies.