Who do you suppose pays for the arrests and cleanup? Yep, have a celebration. Then idiots get drunk, start rioting and causing problems. Maybe someone dies and then the serious crack-down is implemented.
Good-bye party because of drunken fools.
The kids were not rioting until the LEO showed up en-mass.
A firetruck with a watertank could have dosed the small fire and everyone would have remained peaceably drunk.
A simple solution but that wouldn’t have allowed for the local SWAT to use their toys and marching orders.