What if this movie is a secret in-universe sequel to Taxi Driver

It makes a lot of sense if you think about it. Travis Bickle is still living in New York, still alone, but he's changed his name and constructed a delusional past for himself involving a dead wife. But he's still trying to rescue troubled young women from the problems of their lives, especially their attachments to scumbag men.

Also notice how much time he spends driving Anne Hathaway around, and how he knows all the best routes. Would he learn those skills from working in a phone book factory? Not likely. That's his taxi-driving experience showing through.

Also the title of the movie, "The Intern" refers to Ben/Travis' current occupation. Just like Taxi Driver.