Lyon reached the semi-finals with a 3-1 success in Lisbon on Saturday as City were dumped out at the quarter-final stage for the third season running.
Lyon lined up with a 3-5-2 formation, which City matched, but Garcia's side looked far more comfortable than their opponents.
The coach explained to RMC Sport: "You have to expect everything with Guardiola, but we won the tactical battle.
"We have mastered our formation well. We have returned to a hybrid set-up to stop De Bruyne."
Tactics were not the only route to victory, though, with Garcia hailing Lyon's team spirit as they battled hard against apparently superior opposition.
"I'm proud of my troops," he said. "We believed in ourselves. We knew we were not favorites against a big team, but we managed to qualify by scoring three goals and conceding only one.
"It is linked to our collective spirit. We saw everyone working to a high level for each other."
Garcia was also pleased for Dembele, who started from the bench but made a decisive impact.
"It was a disappointment for Dembele not to start, but I told him that he would be very important," Garcia revealed.