Stark did not actually look much younger. Or rather, years of staying up late and running himself ragged with experiments had made him look far older than his peers. On top of that, Little Pepper had not arrived yet, so he looked especially unkempt, like some dissolute rich kid hopelessly addicted to wine and women.
What Strange had not expected was that Stark at this point in time was ten, even a hundred times more irritating than his future self. While dealing with him, Strange had wanted hundreds of times to abandon his plan and simply punch the bastard in the face twice.
Fortunately, he had not studied magic for nothing. At the very least, meditation had given him greater resilience and a steadier mindset than most, allowing him to control his emotions and barely suppress the rage Stark provoked.
Very soon, Strange discovered that Stark's sloppy appearance and infuriating personality were more like a screening mechanism. He did not expose his extraordinary intellect to the world. Instead, he wrapped himself in a sharp shell, and only truly intelligent people could see the gem hidden beneath those awful conditions.
Through several chance encounters and increasingly in-depth conversations, this future, more mature Sorcerer Supreme ultimately got a handle on the still-inexperienced Iron Man. Stark came to regard him as a kindred spirit, and the two became friends.
Strange had once casually mentioned that he had taken psychology as an elective in college and pointed out that Stark might have Anxiety Disorder. Stark neither confirmed nor denied it, and he had no interest in treatment whatsoever, so Strange did not force the issue.
But soon, someone who would change Stark's life appeared: Little Pepper, Pepper. At this time, Little Pepper was youthful and beautiful, capable and fiery.
After taking over as Stark's