I don't think Python was starting to occupy C++ space; they have entirely different abilities. Of course, I am also glad it didn't happen.
The main domain the original team behind Go were aiming at was clearly network software, especially servers.
But there was no consensus whether kernel could be a goal one day. Rob Pike originally thought Go could be a good language for writing kernels, if they made just a few tweaks to the runtime[1], but Ian Lance Taylor didn't see real kernels ever being written in Go[2]. In the pre-release versions of Go, Russ Cox wrote an example minimalistic kernel[3] that can directly run Go (the kernel itself is written in C and x86 Assembly) - it never really went beyond running a few toy programs and eventually became broken and unmaintained so it was removed.
[1]: https://groups.google.com/g/golang-nuts/c/6vvOzYyDkWQ/m/3T1D...
[2]: https://groups.google.com/g/golang-nuts/c/UgbTmOXZ_yw/m/NH0j...
[3]: https://github.com/golang/go/tree/weekly.2011-01-12/src/pkg/...
It was specifically written to measure the performance overhead of a high-level language in kernel, so it explicitly makes the same design choices as Linux: monolithic, POSIX-compatible.
Results look pretty good.
You may have a point that Python would have replaced C++ in those places instead if Go had never materialized. It was clear C++ was already on the way out, with Python among those starting to push into its place around the time Go was conceived. Go found its success in the places where Python was also trying to replace C++.