Pet peeve: the ease of readers declaring that sections of books have nothing to do with anything. People who love to say things like this will very, very occasionally add a "maybe I missed something," but as a rhetorical brush-off; they do not sincerely believe it, and are simply being sarcastic. It's an easy way to sound sharper and more worldly than a writer.

Listen, it's possible the author thought "what the hey" and tossed something into their little masterpiece that had nothing to do with anything. More likely, though, the author and the editor agreed it had significance (and some other readers too). Maybe the author didn't do a good enough job drawing this connection out, but the section is still connected. Alternatively, it's there for "replayability": they don't expect most people to catch it this time, but on a reread, you'll have an a-ha! Alternatively, you were simply asleep at the wheel earlier (or could it be that during the setup, you were convinced the setup had nothing to do with anything, and now you've doubled down?). Alternatively, perhaps you really could have figured out the relevance if you'd thought about it, but instead you decided to stroke your ego and call the author stupid and go about your day. The point is there are several very likely possibilities, only one of which - the least likely - is that the author thought "what the hey" and put random shit in what they worked so hard on.

I repeat: it isn't that it can't happen, that an author can't lose their own plot, or bury their own lead, or fail to dig enough to extract it from the rubble of construction. It happens. But it doesn't happen a quarter as much as readers proudly declare it has happened.

If another reader feels that section is connected and interesting, then the issue is probably you, I'm afraid. Not always. That other reader could be hallucinating. Or maybe they know more - or less. Or they're interested in that bit for independent reasons, and they're simply admiring the scenery, not worrying about or even noticing the fact it isn't pulling its own narrative weight, since they're busy enjoying it. But usually the shortfall will be with you. And we all run into that problem, and it's simply that some readers love to jump right on their soapbox and start blaming the writer when they didn't get something. The rest of us spend a minute and figure it out, and think dismissive readers are being stupid.