The nose of a shark is so jammed full of sensory organs and receptors that if you touch it and push away, like the dude did, the shark wants nothing to do with that pressure and tries to get away. That's why a widespread deterrent to a shark attack is to start pounding the nose of the beast if it gets too close, because it won't like that one bit. The shark was going pretty slow, so it had to ark off to get away from the dude's hand, knowing that a shark can't stop swimming or backtrack.
also, if you've ever seen a shark get put upside down, it goes into a trance like state, so all of this may contribute to the "sedated effect".
Really, this dude knows exactly what he's doing. Like, when that one shark got a bit too nosy, he goes right at it, no wavering, to show the shark he means business. If you swim away and otherwise act like prey would, you'd have been "taste tested" right there, but the guy holds and the shark doesn't test his luck in case the guy attacked himself. The shark doesn't know what to make of this thing in the water, so for all it knows he could be competition.