For example UFC fights can last 10-15 minutes and the fighters have like 1 punch knockouts while real life fights only last 1-2minutes why is that?

I don’t know much about UFC but its entertaining to watch. My question is, what moves aren’t allowed? And if banned moves were allowed and the fight was to death, how much different would the fights look? Would the same fighters/ styles be just as dominant? Would the fighters be more conservative or more aggressive?

I know its a bit of a morbid question but I’m just curious thats all.