They won 90 games and made the playoffs in 2014 and lost in the first round. That happens all the time to good teams. Sure, they could have won a few more games during the regular season with another manager, but they still might have lost in the playoffs.
After that, they lost Scherzer which was what truly marked the beginning of their fall. Cabrera and Martinez got hurt in 2015 and Sanchez sucked and they really didn't have a great team. Then they started shedding pieces.