I don't think it's random at all. From a would-be user's perspective it makes complete sense to me that this post took off and yours didn't get too far. I want to explain why, not to be a dick, but because I feel like all hackers (myself included) have a hard time seeing things from the user's perspective.

First, the title of your submission: > Show HN: Search HN by keywords, user, score, Read online, on mobile or RSS

It's completely unclear what your product is. Honestly it sounds like you packaged up HN with some more CSS and an RSS reader or something? I don't really know. "Read online?" How else would I read HN? "Search HN?" I don't really have anyting to search for, and if I did I would just use Google.

The reason film42's post took off is because people were interested in following. Yours didn't even mention following.

Now let's look at film42's title:

> Show HN: HN Follow – Follow Your Friends on HN

My first reaction? "Oh cool, I have a lot of friends who use HN, I wonder what they've been saying."

Then perhaps the best part of film42's app is that he used HN's styling in a way that almost felt like you hadn't left HN. It is completely familiar, and, as others have pointed out, it feels like something that should have been part of HN already. The friction of onboarding was completely eliminated - I didn't have to sign up for or download anything, but I could use it and wanted more. The missing auth is probably a mistake in the long-run, but missing that feature probably reduced some friction getting started.

At the end of the day, you have 5 seconds to impress me or I'm gone. It's quite possible, when your app doesn't take off, that the only thing you did wrong was not use those 5 seconds.