To be fair, before the aquisition, GitHub was super stable, but also it felt like they rarely changed or added anything.
After Microsoft acquired them, they started rolling out new features at an incredible pace. And if you look at the breakdown of the downtime, most of the downtime is in features that didn't exist before the acquisition.
Though not all of the downtime is in new features. The core is also less stable than ever.
But I just want stable hosting for my shit. I barely even interact with the web UI, other than commenting on PRs.
My (actuarial) read on this is that pre-Microsoft GitHub acknowledged that the complexity inherent in their technology stack imparted a lot of change risk, and that probably informed their decisions around shipping new features.
My (not-so-actuarial 1990's-experience-colored) feeling is that this is Microsoft doing what Microsoft does best, namely including a lot of seemingly compelling features in a product to get people hooked and to keep competitors in a position of trying to keep up.