It's not conspiracy theories, it's any story about a big company doing something bad or evil. Or any story that confirms the worldview of the most active HN commenters.
Any story about Facebook, Instagram, Twitter, Google, Uber, or PayPal doing anything negative tends to bring out the most cynical commenters. HN is usually a skeptical crowd, right until a story arrives that fits their worldview.
The false story about Apple's refund policy that garnered 2000 upvotes before being retracted is a prime example ( https://news.ycombinator.com/item?id=23987584 ). When it was in the #1 spot, several people tried to correct the story in the comments. They were heavily downvoted. For some reason, the majority wanted to believe a random Twitter comment over actual iOS app developers trying to correct the misinformation.
Likewise, stories about psychedelics being miracle cures tend to rocket up the front page despite deeply flawed studies (no control group, usually). Meanwhile any study showing negative effects from psychedelics or cannabis tends to get picked apart for for small sample sizes or the evergreen "correlation is not causation" no matter how good the study was.
The real problem is assuming that HN is somehow immune from the same problems as other social media platforms. HN is very much a social media platform.