The 32-year-old completed an £8 million ($10m) switch to Emirates Stadium on August 8, bringing to an end a successful second spell on the Blues' books.
The Brazil international picked up his first Premier League title in the 2016-17 season and added FA Cup and Europa League winners' medals to his collection under the stewardship of both Antonio Conte and Maurizio Sarri.
Frank Lampard was drafted in to replace Sarri back in June and he immediately set about promoting the younger members of his Chelsea squad into the first team.
Luiz was deemed surplus to requirements, which led to his surprise move across London, but he had no notion of joining the Gunners before they submitted an official bid.
The experienced centre-back has now revealed the real reason behind his Stamford Bridge exit, referencing an "honest" conversation with Lampard over his future.
“I always liked Chelsea, no doubt. I saw a possibility of writing a new story in a new place, but I am forever grateful to Chelsea, to all people, to friendships that are for life," Luiz told TalkSport.
“It was an individual decision made through honest conversation – between me and Frank Lampard, no one else.
“We had a different idea of the future of the game and that’s why I chose to take a new path.
“It’s always very difficult because of the rivalry, but I made the decision to leave Chelsea even before receiving Arsenal’s bid.
“As soon as I decided to leave Chelsea – after a few days – Arsenal’s proposal came, and as it was another great club, I didn’t think twice.”
The former Chelsea ace has adapted quickly to life at Arsenal, taking in eight appearances across all competitions at the start of the season.
Unai Emery's side rose to third in the Premier League table with a 1-0 home win over Bournemouth on Sunday, one point clear of Leicester City and Chelsea heading into the international break.
Luiz and his team-mates will be back in action for Arsenal when they travel to Sheffield United on October 21, before their latest Europa League campaign continues with a clash against Vitoria three days later.