You cant tell me that a 4. place team has only luck and a great Goal keeper. De Boer is clearly the proof that a Coach can be much worser. Im not saying Mancini was good but at last our Team (specialy the first months) looked motivated. Then things tourned out bad for Mancini but also players like Murillo got worse.
But didn't Mancini take over from Mazzari and do much worse that very season? Mazzari was in 5th place I believe, and Mancini took over and we ended up 8th that season, below Sampdoria and Genoa. And that was Mancini who was familiar with Serie A. I'm not saying De Boer is great but it seems you're ignoring Mancini's first 20+ games in charge of Inter, while judging De Boer who's played less than that and had a team that didn't go through proper physical preparations.
I'm not saying Inter had just luck, as we were pretty efficient in front of goal in the first half of that season (pretty much had one shot on target every game resulting in a goal). But the biggest reason we ended 4th were the results in the first half of the season which were largely based on luck.
It's similar to Man U from a number of seasons ago that had De Gea saving them every game.