Even though their Lord had clearly lost (his body turning to ash was a clear indicator of his outcome), many of his loyal (and stupid) Death Eaters were reluctant to turn themselves in and admit defeat.
Greyback was one of the lucky ones who had only been stunned by a member of the Order and then, upon awakening, was able to disappear with everyone's focus on active and fighting Death Eaters.
And now, he was still wreaking havoc upon muggle and magical communities by trying to make several werewolves - whether they be kids, women or men - every full moon and had managed to avoid an auror at every turn.
His towering height wasn't even enough to scare any in stopping them from confronting him, he just managed to get the upper hand so that he had enough time to get away.
He'd be caught though, they all swore it.
Chocolate Frog Card: Wilkes (bronze) - prompts; height, auror, avoid, several