Eight o'clock is hard no matter what network you're on because people have to make a decision to sit down and start watching TV. Every other time slot is a time slot that happens after someone's watching something else.
When you are in the 8 o'clock position, you can either be a cultural phenomenon, or you're endangered. It's a tough time slot.
Once upon a time, something happened, and it was better than something not happening. The end.