I'll try to explain you. Football, like all the other sports on this planet, is not a mathematical equation where you can apply transitive property to its subjects. In poor words: if A beat B and B defeat C, this doesn't mean that surely A is better than C. There are many factors that are important during a football match: the tactics, the psychophysics condition of the athletes in the matchday (maybe someone has slept bad the previous night, or maybe has a bit of stomach ache, we'll never know), the coach and his personal psycophysics condition, the synthony between club mates that in some days could lack while in anothers it works perfectly, etc etc.....There are many factors to keep into consideration because, like I wrote before, sports in general (luckily) are not something certain, like all the activities that involve human beings. These means that of course could happen to win against a team that later defeated the team that had defeated you, and in this case it happened for Inter. I hope I explained myself well.