To see this just as a hosting switch misses the bigger picture. This is the logical infrastructure conclusion of Zig's 'Zero Dependency' philosophy.

Zig spent years removing dependencies on the system C compiler (zig cc), removing dependencies on libc, and is currently working to remove the dependency on LLVM (the self-hosted backend).

GitHub was just another dependency.

For a project obsessed with reproducibility and toolchain sovereignty, relying on a single proprietary platform (and its changing ToS/AI policies) was a massive architectural liability. They aren't just moving repos; they are eliminating 'Platform Risk' the same way they eliminated 'Linker Risk'.