I'm not sure about the pessimism itt regarding our hand. Villain has a joke wide range and was the last one to act otf. He can still sometimes peel 8x and definitely worse kings.
There are two reasons why villain is likely to have a very strong range here.
Partly it is because:
1. We have cbet from OOP into three opponents.
Our perceived range is thus pretty damn strong, so villain is less likely to make light peels. And also, villain does not NEED to defend anything other than a very strong range - since the 'responsibility' for defending against our cbet is shared between him and the two other villains.
But much more importantly:
2. It is to do with villain's preflop range and how this interacts with the flop texture. He is an aggressive regular who has overlimped after two weak players have limped. So what does he have? Almost exclusively he has small pairs, suited connectors/gappers, and perhaps some other raggy suited stuff like the odd K7s or whatever. He is not going to have (m)any broadway cards (suited or offsuit), and he is
very unlikely to have a hand like 87 offsuit or K6 offsuit.
This range either smashes this flop (a flush or a set) or completely whiffs it. There are not many partial hits. Yes, he will have a small amount of Kx and 8x hands on the flop - but combinatorically not very many. Especially given that he would raise a lot of Kx hands preflop, and that he is not going to have any offsuit combos of 8x and in fact very few offsuit Kx combos. Plus, given point 1 above, he might well fold the flop with the small number of 8x hands that he has. He can't have hands like TT with

or Ah6x or KJ etc because of preflop.