Dude with exact stride cadence blew past me the other day...why?

Am I missing something? I was on a run with Billy a few days ago and on the tail end of my run there was this guy who I heard coming up behind Billy and I. I could hear his footfalls and I realized that they were falling at the exact same time mine were. The guy caught up to us and quickly passed and put distance between us. I watched his feet and it was like we were mirror images in terms of footfall.....why was he so much faster than me? Is it stride length or something?...I want to run that fast.