You have to plug in the cable somewhere. If the hardware where the x-connect is plugged in dies, has issues, has to be rebooted, etc. you have an issue and it's not like there were no CF issues ever.
Their problem was that they only have two transit providers, and one of them black-holed about 3-5% of the internet. Since it was a routing issue, I'd guess it was either a misconfiguration, or that the traffic is being split across dozens of paths, and one path had a correlated failure.
All the redundancy in the world can’t protect you from some random person digging in the wrong place.