I think you should ask the reverse: What was unique about that time period that created these spectacles?

Entertainment and fighting have always existed (and still do), but usually not to the death.

> and still do), but usually not to the death

It usually wasn’t to the death in ancient Rome either. Unless your were being executed.

I don’t think that the violence part was unique in any way, Romans were the first commercialize it and scale it up to such an extent though.