>Why do you think Windows is currently such a mess?
There have been some writings and posts here about Microsoft. Here is one from last spring, from a guy that was long time Windows core developer and moved to Azure group. It's well worth reading, what he writes about challenges they have had and most likely still have if not even worse now.
There was a great article awhile back that shed some light on just how dysfunctional azure is as a platform: https://news.ycombinator.com/item?id=47616242
If I had to guess it's because Github is sitting on top on infrastructure held up by toothpicks and duct tape