Who ARE they ??

"Travellers"...WTF..is it some kind of Irish clan, secret society, or are they akin to gypsies or something (would explain the gypsy squalor they seem to choose to live in)

So he was one of them, and he gave up his house, and went back to live in a mobile home trailer wtf witn them, why, to cash in the balance of the house value towards his boy's medical expenses, or just because he needed to live with them to qualify to fight in the 'Pug" or wtf it was..to win money for same said project?
How much money was up for grabs?

WTF were the envelopes thick with cash being handed back and forth, and around in circles?
Why did people then begin scrawling abusive graffiti around the camp?
No clue what that was about..was it payments to 'the council" ? lol..

My main complain were not really the sickening violence, or the implausibly weak capitulation at the end of the previously apparently unbeatable O'Driscoll (even though I'm glad the psychotic subhuman got knocked out, it was not served up or choreographed in a very believable way) ..my main complaint is just,

WTF was the entire bloody muddy mess actually about ?