The police should have gone in and ordered them to turn off the amplification, and removed it if necessary. But there would only have been a few police officers available, in rural Somerset (?), and with 3,000 people attending they probably felt discretion was the better part of valour. Arresting the organisers will be nigh on impossible as it was illegal. Not right, but very difficult to summon up enough manpower without preparation. And of course the participants will be lined up with phones ready to record every move.
It reflects very badly on our young, who having survived covid lockdown feel they are entitled to do as they please.
Suffered several 'folk festival' weekends held near my house; it took several years and a whole community effort to close it down.