I think it lies at the intersection of a lot of topics where HN comments are hostile: VCs, large fundraising, AI, OpenAI related employees. These are all topics where HN comments are more hostile than pragmatic.
Most of the hostility is just a proxy for “VCs bad” banter.
In the case of a bubble, hostility is pragmatism.
Of course, nobody knows that it's a bubble, but nobody knows it's not a bubble either.
Many people know it's a bubble. You see lots of HN comments that it's a bubble. We certainly did in 2007.
In a bubble, the predominant notion is not "I wonder if it's a bubble", but rather "It's a bubble, I hope I can make my money before it pops". A perfect example of this was the Tulip craze in the Netherlands. Nobody actually believed tulip bulbs were worth that much, they just wanted to find a bigger sucker to make a profit, if you read accounts from the time.