The article lists a lot of facts, but it doesn't actually explain what happened.

IE, it explains what DNS is, but it doesn't explain why the outage happened. Instead, it merely gives a timeline with a lot of context that's useful for someone who's still learning about what DNS is and how it works.

Thanks, this is really helpful. I had not even realized that every DNS query for .us (for example) goes through a single root registry before going to the actual nameservers.