Klopp watched the Champions League clash from the stands as he served a one-match touchline ban but enjoyed a stress-free evening, with Dortmund running out 3-0 winners thanks to goals from Robert Lewandowski and Marco Reus.
The BVB boss believes that his side's commitment and drive proved the decisive factor, insisting that Dortmund were willing to work harder than their opponents to secure all three points.
He told the club's official website: "The team executed perfectly what we talked about before the game.
"Marseille are a strong side if you let them play their game. We needed to prevent that by putting in a lot of effort.
"We had to put in a lot of effort, and if we'd run just a few kilometres less today, we would have struggled. We had to give our all. Now we are in a good position in our group."
Dortmund are now level on points with Napoli in a Group F topped by Arsenal, ahead of a trip to the Emirates in three weeks' time.