Giroud came off the bench with Arsenal trailing 3-2 in Friday's Premier League curtain-raiser at the Emirates Stadium and after fellow substitute Aaron Ramsey equalised, he headed in an 85th-minute victor.
"I felt that to lose tonight would have been awful for us because we had such good preparation and to sit there in the morning and think we had lost at home would have been bad", he said. At one stage I opened the door for him to go as I knew I had many strikers, and in the end he chose to stay. He's a fantastic player, but as well he has a big weight in this squad.
"To be honest, there was something in my soul and in my heart which told me to stay", he said.
An admiring Wenger said Giroud was "in his prime" and "at the top of his game".
The future of Alexis Sanchez is unclear but Wenger has suggested he is prepared to keep the striker for a season and then let him leave on a free if he will not sign a £300,000-a-week contract.
"I opened the door for him at some stage [to leave], because I know that it's important for him to play", Wenger said in his postgame news conference. "He's a collective player and an intelligent player".
"We went for a win and we deservedly earned it". "We had some avoidable goals which we conceded and overall we have to work on that", he said.
The first touch from the 60 million euro (US$71 million) signing was at kick-off.
"Obviously I knew that I was going to have a chance so we tried to push".
"There were hard moments when we were down and we managed to get out of that and it's great to see".
But he drew encouragement from his side's display.
"Scoring three goals away from home is a positive and we'll get back on the training field to make sure we sort the problems out".
Britos stabbed home at the death after Liverpool had come from 1-0 and 2-1 down to lead 3-2 thanks to a three-minute blitz in the second half, when new signing Mohamed Salah made his presense felt.
With what will surely be the first of many Lacazette has already got his first Arsenal goal in his first Premier League outing, joining Freddie Ljungberg, Emmanuel Adebayor, Samir Nasri and Thomas Vermaelen in doing so in the Wenger era.
He added: "Our character was great because we were twice down and came back".