in my view it was because there was no ref intervention when the incident happened, valeri simply let the teams play
same goes for the penalty given by var during the milan derby the other day
btw this is a rule that can be bent apparently, because there were a couple of incidents when var called for an on-field review in similar cases. so yeah, this is a stupid rule, and isn't applied with 100% consistency, but at least you can debate it for hours after the match