There are many factors that play a part in each match. There is no way to predict the outcome for sure or to say exactly why a particular match ended the way it did. But here are a few things to consider:
To win a game you should try to control the most quadrants. The colours of the quadrants in the newspaper report show how many and which ones you or your opponent controlled. Additionally, you have the option to view this as a percentage.
The players' skills are another important factor. They affect a player's strength for his position and have some direct influence in many situations of a match.
The game engine is based on probability calculation. The skills of opposing players are taken into account for these calculations. The better the skills are, the higher the chance of winning. This means a more skilled player isn't automatically winning each duel, but the majority of the duels during the match.
To sum it up: the formation, tactics and effort you and the opponent set, decide how many chances a team will have during a match, what kind of chances they are, as well as how great the chance is, that an action results in a goal. But even if you have an 80% chance of getting a chance in, it can fail, even 5 times in a row, with very bad luck. And if your opponent only has a 10% chance of getting a goal, it can succeed, also multiple times in a row, again with a lot of bad luck on your side.
Therefore it is possible that a stronger team loses a match against a weaker one (i. e. strength 60 vs. 40) if both are using a sensible formation and strategy. The bigger the difference, the harder it is of course. But if they played multiple times unchanged against each other, the stronger team would show its superiority by winning a lot more often. And not being able to fully predict the outcome of each match is highly desired, as it keeps the matches exciting for both teams.
Strength value shown for the club and each player is only a basic indicator of the potential that player and club have. It is possible to lose a match even if the strength difference between two clubs is clear.