windmill1
As to why they did it, I doubt even they know - so thick are they.
A policewoman friend did once tell me that she often got to hear the three stock replies that suspects routinely come up with when they admit what they did and why they did it.
"I was bored" or "I did it for a laugh" or - the worst one - "I don't know".
Ye Gods!
Disaffected, angry about the caravan, wanting to hurt/spoil, maybe prove something to each other, get anonymous attention through notoriety - and thinking they would get away with it.
For me any sentence would include hard reparative work, the trouble is prisons don't offer this and would community schemes currently available fit the bill?