Forgive my ignorance, but how do things like this happen at such a massive scale? I would understand maybe one big area shutting down because of some sort if internet network issue, but then there should be some redundancies in place no? I don't get how it just all goes down across the globe, is there one master-computer that has just gone down, taking everything with it?
The saying goes, "complex systems fail in complex ways". Check out some of the cloud provider postmortems here for a few fascinating and detailed examples: https://github.com/danluu/post-mortems
You could say certain failures only occur and cascade under Special Circumstances. :)