If you're talking about nuclear war, I don't think you could expect Polymarket to pay out in the aftermath. So anyone betting on one would be pretty dumb.
I think that GP is saying that recent betting market developments provide evidence that Trump or someone high up in the administration is tipping off others. Therefore, one might think that the 'in' crowd would be tipped off about an apocalyptic event, which would trigger this software. I don't think that GP was saying anything about betting on an apocalyptic event.
You can currently bet on Jesus returning before 2027, which means they would also have a hard time paying you, and 4% are betting on yes.