Atletico were 4-0 ahead at halftime through an own goal from Eric Garcia and efforts from Ademola Lookman, Julian Alvarez and Antoine Griezmann.
That scoreline remained for the first-leg triumph and Simeone said afterwards: "We found an incredible energy in the stadium. Life is energy. We were able to ride that wave of energy.
"The interpretation of the game was very good, with the four forwards reading the space very well. Other days we say we lack decisiveness, but today will be remembered for how we played. They represented it in the best way."
He also said, "We've had some important nights. I remember the Champions League match against Barcelona. But the energy comes from the stadium, then we interpreted the game as we had to play against a difficult, tough opponent.
"Even with their absences, they're always a force to be reckoned with. We played a very good match."
On Alvarez's performance, Simeone added: "I repeat, the assist to Lookman was fantastic. Julián has the goal-scoring touch and thank God he's back and I'm sure he'll keep it sharp for everything that's to come."