My first instinct would be to guess that something like this happened because of some intentional and well-meaning effort to upgrade some critical part of their

My first instinct would be to guess that something like this happened because of some intentional and well-meaning effort to upgrade some critical part of their infrastructure. Just my hunch given that it happened during the middle of the week in the middle of the day, and came back relatively quickly. The quick but not instantaneous bounce back has the hallmark of someone following a carefully laid out worst case contingency plan. I look forward to the postmortem.