He didn't get sacked because of bad results. He got sacked because it was convenient. The sacking paved the way for the return of Jesus and an investment of 100M right before club elections.
Jesus just finished 3rd, lost every competition, even a final to Braga, and the club invested 100M in players last summer, with no improvement in the played football. He's not getting the sack because it's not convenient. The president bet his life on this and lost, but Benfica is his only salvation from going to jail. He's part of a series of legal proceedings. Just two weeks ago he was heard on a parliamentary commission due to loans with the bankrupted bank BES. A former banker, in the same commission, admitted LFV (Benfica's president) would not have gotten the loans he had if he wasn't Benfica's president because he has no assets to cover. So you know, his loans [private loans] are up to 300M.