Once moviegoers get a chance to see the film for themselves, they'll understand why.
The movie chronicles the true story of Saroo Brierley, a man who searches for the birth mother and family he was separated from when he was a young boy living in India. To do this, Saroo (Patel) attempts to find his home town via Google Earth from Australia, where he was raised after being adopted.
If that sounds like a daunting task, it's because it is. Saroo pushes himself to the emotional brink in hopes of finding the life he only recalls through a 5-year-old's eyes.
"[I was] just astounded that these words I'm saying, this journey that I've just read is real," Patel told CNN of reading the script for the first time. "It's just so incredible. It's a feat of humanity, of what he achieved."
Preparing for the role was an 8-month process for Patel, arguably best known for his work in 2008's "Slumdog Millionaire" and "The Newsroom."
He had to learn an Australian accent and also set out to bulk up his frame. He hit the gym at director Garth Davis' request, who wanted to show Patel as he'd never been seen before.
"We spoke about the look and growing the hair and going to the gym and getting a bit more Aussie, a little more Alpha," Patel said. "Eating a bit more food."
Seemingly the hardest aspect of prep work had nothing to do with his physical form.
Davis had the cast do significant work on what Patel calls "introspection." Patel was asked to keep a diary and at one point was asked to sit alone in front of the mirror for an hour looking at his reflection.
"All sorts of crazy stuff," Patel said.
Then there was his visit to the Indian orphanage at which the real-life Saroo once lived.
Patel recalled being greeted by a message written in flowers on the floor: "Welcome Lion."
As he walked around, Patel said the kids would call him "hero," referring to his role in the film. That, he admits, made him feel "like a fake."
"You're like, 'I'm not the hero. You're the heroes,'" he said. "The one I went to, [some children] are severely disabled, suffering from all sorts of muscular dystrophy and things like that and in so much pain. And the staff, a lot of them are volunteers."
Patel wrote about the visit in his assigned diary, he said.
"You see in an environment like India where there is a lot of chaos and madness, these beacons of positivity and hope," he recalled. "It's amazing."
"Lion" opens in theaters November 25. Patel hopes the themes of family and unity come through.
"Everyone keeps saying you want to call your friends or your sister or your mother after this," he said. "And that's the message we should be putting out in to the world, especially at this time."