I actually think, someone could very well have an 8 here. Sure UTG+1 should not open many 8X hands if any at all. Maybe A8s, 98s, 87s, and then he is already opening wide. But as I understand it, people are typically playing to many hands in low stakes live games, so I certainly think, this is possible.
And when he only had to call a click-it-back 3-bet, nothing was removed from his range. I also think, it makes sense for him to just get it in, when Hero makes a pot sized donk bet. It is a draw heavy board, and if Hero is donking a hand like JJ, many cards could scare Hero later. Even so if UTG+2 had folded, I would still snap call the jam from UTG+1.
However when UTG+2 then also jam, and possible for a much larger stack (depending on Heros stack), this is where, I dont like the spot any more. UTG+2 is obviously a wildcard using an incorrect 3-bet sizing, and when someone does that, I will typically assume, they are not very good, and that they are messing around with a wide range of hands. So in my opinion UTG+2 can have 8X quite a lot, and this is why, I am folding as played.
This is also why, I am never just flat calling preflop. We are way ahead of both players range, and we are out of position, so flatting just make postflop a hell, which this outcome is a good example off. Low stakes poker really is stupidly simple. When you are likely to have the best hand, then bet or raise. That is pretty much all, there is to it.