The article says it is the second outage this week, but at the end of last week some Email related services also were down. I think products like Sharepoint were affected the most and the post mortem is still pending.
Looks like some restructuring of infrastructure. Would be welcome if speed across O365 would increase.
I am surprised to see no mention of COVID and if perhaps the increase in remote work is taxing Outlook and other Office 365 services more heavily than expected. It would be an easy way to wave away some of the outages.
Increased load on e.g. Teams from widespread customer adoption of WFH did pose a challenge at the start, but they absorbed the load fairly well (some other workloads were de-prioritized) months ago.