Such surprising and unexplainable results do occur at times. But if you want constructive feedback, post your opponent's formation, yours as well, your tactics, if you made any changes during the game and a screenshot of the statistics table. Only then will we be able to understand why things went down as they did.

I just met an opponent a couple of percent weaker and won 7-1. Yesterday I met a team 4 % stronger and won 5-0 and another 34 % stronger that ended 1-1. It's not impossible if you're able to read what your opponent is doing and take advantage of his weaknesses. Then there're times I've lost to +20 % weaker teams. Mostly it's about preparedness.