> Why couldn’t the core team and the core-adjacent PyPA make a tool as liked as uv

Incredibly large backward-compatibility burdens [0], internal politics [1] and general institutional dysfunction (no footnote; if you're familiar then you need no explanation, and if you aren't then the less said the better). Nothing to do with Python as a language. Most of the important pieces to get uv-like performance are algorithmic choices, and most of the rest are available as built-in C code in the reference implementation [2].

(Edit: wait, I recognize your username. You should definitely know these sorts of things.)

> why is the Python package manager uv written in Rust and not Python?

Because that's the language that Astral devs like, and because installing Python itself is considered in scope for uv so there would be an intractable bootstrapping issue.

[0]: In particular, the entire model of `setup.py` defining metadata is certifiably insane, especially when you consider the projects that expect to feed that code to Setuptools at build time in order to figure out what version of Setuptools is needed at build time. But this legacy approach is seen as something that absolutely must be guaranteed to work for well beyond even now; even attempts to remove long-deprecated, minor aspects of that functionality end up breaking major projects, including ones that didn't even require a build step in the first place [3].

[1]: Most obviously, GvR not wanting to have anything to do with it when initially approached by the SciPy people in IIRC 2011, leading to the creation of Conda). But a lot of other things, too. The backwards-compatibility issues synergize with this; consider for example the architectural dumpster fire of Setuptools, and the timeline of distutils removal from the standard library.

[2]: See e.g. my analysis in https://zahlman.github.io/posts/oxidation/ .

[3]: See e.g. my LWN article https://lwn.net/Articles/1020576/ .