There are backup provisions. Disney's systems are distributed. Clearly, what happened in this case was that both the primary and the backup failed. There is a limit to how many levels of redundancy is appropriate for a ticketing system, as compared to a system that stores PII, and as compared to a system that when it fails people die.
I can't really argue with that. I'm curious to know what their BC plans are around this, seeing as how this is kind of a critical system (Maybe I'm wrong, but...).