alt Hacker News> then something must have changed just prior to that
Not at all, they could have simply hit an unexpected behavior for their infra they hadn't seen, tested, or expected before. Global scale infra gets very, very complex, and tbh this is Microsoft... they're not very good at it.
Unexpected behavior doesn't happen out of the blue, it's not LLM, these are deterministic systems. It's usually config change or code change, not necessarily in the component that's misbehaving, but it is somewhere.
More often than not, it's DNS :)