Money, marketing, the opportunity to be the face of a franchise in a major city -- they all likely played a role.
But so did Amar'e Stoudemire.
Anthony says the chance to play with Stoudemire was "one of the reasons I wanted to come to New York."
So it's difficult for Anthony to watch Stoudemire struggle with another knee injury.
"As a friend, it's hard for me to sit back and act like it doesn't bother me because I know how hard of a worker he is [and] I know the time that he puts in the gym to train and rehab," Anthony said Tuesday. "To see him go forward and then take some steps back every time, it's just sad."
Stoudemire will miss at least the Knicks' first three preseason games as he works his way through another knee ailment. The 11-year veteran is working his way back from a knee procedure over the summer -- his third in the past 12 months.
"I'm still getting stronger, still getting the legs strong enough to withstand the pressure of playing, but progress has been great so far," Stoudemire said.
The six-time All-Star was limited to just 29 regular-season games in 2012-13 thanks to two separate knee procedures. He also had microfracture surgery in 2005.
Anthony sometimes wonders whether he'll ever get to play with Stoudemire when he's 100 percent healthy.
"Yeah, I think about it. I think about [it] sometimes," he said Tuesday. "He was one of the reasons why I wanted to come to New York. So for me not to have that chance, the opportunity to get a full season in and get a rhythm going with him -- it's not something I thought would happen."
Critics have continually questioned whether Anthony and Stoudemire are a good pairing. Both players like to operate in similar spaces on the floor and seem to hinder one another at times.
The Knicks are 45-44 in the regular season in games in which Anthony and Stoudemire share the floor.
They are 2-11 in the postseason when Stoudemire and Anthony are on the floor together, although the Knicks' 1-2 mark last season is a bit misleading because Stoudemire was playing limited minutes.
Recent statistics aside, Stoudemire still believes he and Anthony can play well alongside one another.
He's also proud of the improvements the Knicks have made during his tenure.
"Since I've been in New York, we've made great progress for the organization. We are a team to watch. We have more TV games now than we had before. But on top of that, we've been to the postseason every single year," Stoudemire said. "And that was a part of my goal of coming here: to build something that will allow us to improve. Unfortunately injuries played a factor after I was here that first year. But I do envision myself getting healthy and being able to dominate as I once did before."
When he was healthy, Stoudemire played well for New York last season.
He averaged 14 points and five rebounds in 23 minutes per game.
Anthony hopes Stoudemire can do the same for the Knicks this season.
"It's another weapon that we need," Anthony said. "We could have used him last season at certain points. For him to get a fresh start off of this season, we need him. He's a big key to this team's success."
Anthony just hopes Stoudemire can return to the floor at 100 percent health this time around.
"Because one day he's here with us and another day he's back rehabbing and training and trying to get right," Anthony said. "I think for him, I'd rather see him get back all the way right."
Ian Begley is a regular contributor to ESPNNewYork.com.