I just assume that they drive by places randomly, decide they want to wreck them, and nothing anyone could ever do would ever be able to stop them from running through every wall and spin-kicking every piece of glass in whatever place they have decided needs to be wrecked.
So you might own a slightly run-down but still perfectly functioning bowling alley, but they just show up one day unannounced and start destroying the place. And you probably get mad and want to stop them, but what are you going to do? These guys are literally World Champion class professional wreckers. The guy who claims to be a scientist or some shit probably just tells you that, look, they're going to wreck your bowling alley and there's nothing you or the police or anybody can do about it, so just take some money and pretend to be OK with it for the cameras and please, please don't make them mad. Not again.
I do think it's kind of a rip-off when they run into something (again, often literally) that they can't actually wreck, and they just kind of turn it upside down and decide that counts as wrecking it. I don't care if something is made of solid steel, the younger brother should have to keep running into it as many times as it takes for either the thing to be wrecked or for him to die. I think he'd be OK with doing it, too, if they presented that as an option.
Their parameters for what they do and do not break are poorly defined, as is what constitutes being broken. The last one I saw, they trashed a movie theatre (a perfectly good movie theatre, near as I could tell). And they busted up the projection room, to the point of destroying the wall that separated it from the theatre itself. But they didn't destroy the floor of the room. Or the walls of the theatre itself. If they're gonna "wreck" a place, to me that means the place is completely leveled.
As far as dying goes, there was one where they did a bar, and they had to smash the big piece of slate that used to be a pool table surface. The science-y guy on the show notes that slate breaks jagged and extremely sharp, so they could very well sever a femoral artery or even amputate a leg while trying to break this thing. Would you ever do anything in your life that carried with it a 10% chance of instant amputation?