Joachim Low's Germany thrashed Brazil 7-1 on Tuesday in Belo Horizonte with the Europeans striking five times in the opening half-hour.
With a 5-0 lead at the break, Germany were keen to stay focused and ensure Brazil did not gain some traction early in the second half with a quick goal or two, according to Hummels, while the Borussia Dortmund defender also claimed Low's men were wary of showing off against the hapless hosts.
"We just made it clear that we had to stay focused and not try to humiliate them," Hummels said on Wednesday.
"We said we had to stay serious and concentrate at half-time. That's something you don't have to show on the pitch if you are playing.
"You have to show the opponent respect and it was very important that we did this and didn't try to show some magic or something like this. It was important we played our game for 90 minutes."
Hummels claimed that the semi-final thrashing - the largest win in a World Cup knockout match since the introduction of a group stage - could be explained by a combination of unlikely factors: Brazil became completely disorganised and Germany were close to perfect.
"After our second goal they got confused," the 25-year-old said.
"They were not organised on the pitch and after that we didn't miss a chance until we scored the fifth goal. This doesn't happen too often. You just have to enjoy it."
Hummels added that Germany are well aware their victory over Brazil will not guarantee a world title in Rio de Janeiro on Sunday, when they will play Argentina at the Maracana.
"We know we are one of the best teams in the world but you always need a bit of luck and for us it was a good day (against Brazil)," he said.
"We must enjoy what happened but if we lose the final, this semi-final will not be worth anything.
"The game does not have any impact on the final on because it will be a totally different game. It was nice how it went but it will be no problem keeping our feet on the ground."
