Nexus Blitz - Battle Prize

Idk Why Battle prize works like that. i just won 2 first rounds and lost event. first round went super clean, both of us had almost full hp. second round was close and only one left with qaurter of her health. they enemy won it prety ez since she was almost dead, and he won the next one because our fifth was bad. so at the end we killed 4, they killed 3 and they won the event. why does it workes like this.