Do these people not know how their own system works? Shouldn't you be able to look at the state of your server? Is it resource starved? Run out of ram? Processes hung? Too much network traffic? Too much swapping? Crashed? BSOD?
"...Current status: While the servers we've returned to service initially remain healthy, we've observed that they can become unresponsive again once they begin receiving traffic. We're analyzing diagnostic data from these servers with our networking and platform experts to determine what's triggering this behavior.
..."
https://status.cloud.microsoft/m365/referrer=serviceStatusRedirect
@ai6yr having worked on systems like this, it can be remarkably difficult to understand their state. They've typically got many thousands of person-years put into their creation and understanding the full stack is not possible within a single human lifetime.
You depend on abstraction layers, alerting systems, and runbooks, and when those fail, it can be really thorny to fix things. Especially once many of the people who created the system have left and you've lost a lot of the institutional memory of how it was built.