"Is it possible that, at some point in the past, large audiences were entertained by watching bloody armed fights to the death"
Huh. I'm honestly a little mixed up by this one, they usually have the "is it possible that this happened?" Sort of questions are for their completely crazy bullshit ideas. They switched it up on us, normally they'd lead with the nonsense about the very well documented goings on of the Colosseum being used as a power plant.
But, aside from the well documented use as an arena, who has ever said the arches and columns were "purely" decorative? They are designed to support the building, Rome was famous for their great use if building materials and arches. And yes. People do love watching fights. Movies, tv shows, games all revel in violence. Actual martial arts like boxing, MMA, Muay Thai, Knight Fights, scripted fights like Pro Wrestling, to stuff like mentioned above, things like Battle Bots or Robot Wars. People LOVE watching fights and fighting.
The bigger questions that rule against it being a giant power plant would be the obvious ine above, why did all contemporary writings describe it as an arena? Why would you have a power plant that could sit 50-80 thousand people? Why would you have a retractable awning for bad weather? Why would you build it to hold water? Where all the arenas all over the Empire just smaller power plants, even with the variations of construction? Where did the power go? To the fire lit rooms? The slave powered field equipment?