Benfica should be able to understand Jose Mourinho if in the end they were defeated by Chelsea because after all he had just been appointed as a coach and certainly needed time to manage the team to be better and directly facing Chelsea was of course a very tough challenge for Jose Mourinho even though Chelsea was his former club but Chelsea's performance had improved so Jose Mourinho no longer recognized the strategy used by Chelsea currently.
Not only Benfica, many out there are yet to come to this realisation and so they do throw tantrums at Mourinho because they expect some kind of magic from him at once forgetting he can only do within a certain capacity at a time, he has not spent upto a season and yet the expectations be so high that even against top European teams, they just make some unrealistic expectations, the current for of Chelsea is such that even with the time, Mourinho may not be able to still meet up because they have a continued improvement progression.
He'll be taking over as a new manager for Benfica, but as you said, it's not right to expect him to suddenly wield a special magic wand. He'll get to know the players as much as he can and put the best players on the pitch. I believe he did his best in the Turkish league last year. Furthermore, Fenerbahçe's 18-year-old Yusuf Akçiçek's career took off thanks to him. Mourinho is a successful coach, providing young players with the opportunity to introduce them to the world.