Firstly, Brazil were missing their star player Neymar, and their captain Thiago Silva. This meant that Fred had to do a lot more, as well as the defenders and Julio Cesar were under constant attack without Silva. Germany played beautifully, and there was nothing the Brazilian defence could do.
Of course, Brazil still worked aggressively, which is how most teams seem to play nowadays. However, the German defence (read: Lahm and Neuer) easily took care of Brazilian attacks and quickly coubterattacked.
Also, when one of the Brazilian defenders got the ball, instead of Muller or Krose pressuring, Khedira came from behind and overlapped. This means that 3 people were on the ball deep in the Brazilian side. Therefore, one slip up from the defender lead to an easy goal, despite Cesar's efforts.
TL;DR. Germany are the better side tactically, and Brazil didn't gave a leader so it was an easy victory from Germany.