How is this possible..

[MissFushi]

YouTube is about as predictable as the waves during hurricane season. If there is a reason his did better, study his video. Look at the comments he got, the number of likes and dislikes, the thumbnails and title. Find out what made it 'better' than yours. It could be luck or something was good about it.

 

[Uncivilized Elk]

If you just started out on YouTube there is no such thing as luck.

That's incorrect. Depending on what your video category is, it could be nothing but luck. Most people would agree luck is most variable just after starting out than at any other time.

And that's my answer for this thread.
Assuming you're right and he did nothing special in terms of sharing or whatnot, the algorithm game treated him super well and he got his video placed somewhere nice on YT and it got a lot of clicks.
Ask him to check his analytics and see where the traffic is coming from, that would help in answering your question.