In the grand scheme of things the difference between C, C++, and Python isn't meaningful when operating over a network (edit: for a single-user system). It's very likely that the difference for thread OP is just caused by weaker connections to specific repos.

We're talking about a package manager, not a game, network server, etc. On a basic level the package manager only needs to download files from a network and install them (OS syscalls for reading/writing files, these are exposed C functions or assembly routines), or delegate to a specific package's build setup (which will also likely be written in a compiled language)