The reason is a bit strange. To me it seems as if Zig is just very opinionated. Personally I think the decision to move to Codeberg was made independently of Microsoft being a problem. I don't dispute that Microsoft is a problem; I just don't see many great alternatives to github either. Gitlab consistently is worse for me as a user.

I think the bigger problem is that these big megacorporations control so much. I find Google even more problematic than Microsoft these days in that regard. AI worsens this problem, but even without AI it already was a problem.