The £85 million midfielder made the move from West Ham this summer, and although Tottenham have taken just one point from their opening three league games, sitting 17th in the table, Fernandes says the club's project convinced him to turn down interest from elsewhere, including Manchester United.
Fernandes has featured in three of Spurs' league fixtures so far, starting one, and says his conversations with head coach Roberto De Zerbi were central to his decision to move to north London.
"I spoke with the Mister and he was the key for this decision," Fernandes told Sky Sports.
"You can feel the energy and the passion for football when you speak with him."
The Portugal international, who has signed a contract with Spurs running to the summer of 2031, said the Italian head coach's enthusiasm was obvious from their very first meeting together.
"The first day of pre-season, I met him and he was very happy. I was also very happy to get to play for him. I said, 'Look, I chose Tottenham because you were one of the most important reasons'."
Fernandes also praised De Zerbi's methods on the training pitch, having initially been chased by several Premier League clubs before Tottenham won the race for his signature this summer.
"He's a top coach. It shows both on and off the pitch, and I'm very glad to get to work with him."
The 22-year-old, full name Mateus Gonçalo Espanha Fernandes, came through Sporting CP's academy before a loan spell at Estoril, then made his name in the Premier League with Southampton and West Ham, ranking among the division's top tacklers last season with 103. Manchester United and Liverpool were also credited with interest before Spurs won the race for his signature.
Fernandes also believes the quality around him at Tottenham can lift his own performances further. Spurs face Everton at home in their next league fixture on Saturday, with De Zerbi, who has previously managed Marseille and Brighton, still searching for his first Premier League win in charge.