The Brazilian made his first official appearance for Arsenal on Sunday and picked up a trophy in the process, starting as the Gunners beat Manchester City 3-0 in the Community Shield.
Speaking to ESPN Brazil afterwards, Guimarães gave his first public explanation of why he felt the time was right to move on from St James' Park.
"I spent almost five years at Newcastle. And I believe I helped rebuild the club," he said. "I arrived at what, in my view, was one of the most difficult moments in the club's history. My family and I decided to try something new."
Guimarães joined Newcastle from Lyon in January 2022, when the club was still fighting to stay in the Premier League following its takeover, and went on to become one of the central figures of the team's transformation, eventually taking on the captaincy.
"I'm very happy with the opportunity I have here at Arsenal. Now it's about continuing to work," he added. "I'm very happy to have started my first official game on the right foot, and winning a trophy was very important."
The 28-year-old's comments carried no bitterness towards his former club, framing his Newcastle spell instead as a successful chapter that had simply run its course. Arsenal signed Guimarães for £75 million, making him the fourth most expensive Brazilian footballer in history according to ESPN Brazil, in a deal that pushed Newcastle's summer player sales past £240 million.
Looking ahead, Guimarães made clear he expects his new side to challenge on every front, with Arsenal having ended a 22-year wait for the Premier League title last season before reaching the Champions League final, where they lost to Paris Saint-Germain on penalties.
"It's a very strong squad, with great players," he said. "I think that's the intention – to fight for everything, and we're going for it."
It proved a fitting start to his Arsenal career: a first competitive start, a 3-0 win over Manchester City and a first trophy in the space of one afternoon.