Battlegrounds. How?

I feel like I need a PhD in mathematics and physics to figure out how to play battlegrounds mode. I won 2 fights in a row and still lost the match. Why do you have to make it so complicated and imo unfair?
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You get 30000 points for the amount of health you take off the opponents champion. 0 at max health and 30k at no health left. Take more hp off them earn more points.
You earn up to 15000 points for the amount of time it takes to complete the fight. Take less time earn more points. Take more time or die lose points.
Winning a match does not matter to the points earned. More points win not first to kill the others champion.
It really not complicated, highest score wins each round, that simple. Whoever wins 2 rounds wins the match.