It depends. People were speculating that exchange online protection was hit with a DDoS attack, which could have made it difficult for automated backup systems to come online.
I definitely read the article. Even after ready what you quoted I don't get why engineers had to do anything and why it took 4-5 hours or whatever time. Load balancing, failover, all these services were created to be automatic. Surely Microsoft had the resources and money. So I'm curious wth really happened!
Now most companies aren't going to publicly admit to a DDoS attack so we may never know.