Obviously not authorized to release more details than have already been made public, but when the book hits the real world sometimes you find new failure modes, software has bugs, or humans find creative mistakes. It's also very hard to build global scale systems with zero possibly of global failure. But every time a crack is found, you learn something and do what you can to eliminate the whole class of related failure modes.

Disclaimer. I don't work on the thing that broke here but I am in SRE. Speaking in broad generalities.