It was probably a call made weighing the backlash. Crimes against property are often viewed as being victim-less, so going in and giving some hickory haircuts would make the cops look like the bad guys. By standing back and hopefully video taping to identify the ring leaders, the university can now move against the perps without having to look bad in the news.
Not saying the decision was the correct decision, just speculating on the decision process.
When vandals set the standards for the community, we are all victims.
That goes for graffiti 'art' or destroying public or private property.