If weak team has no chance to win strong team, it will be no fun to play this game.

Your team is clearly weaker in quality. In such case, if you never thought you can win AND you did not prepare to make this match as close as possible, I will say you win due to pure luck. We may try to explain the factors leading to the result, but in your angle, it is pure luck.

BTW, if you want some managers here try to analyze the result, I think you may give more information like the natural positions of players of 2 teams, match highlight, etc.