I don't know your background, so I don't know at what level I should pitch my reply.

At the time, as far as we know, no one in the world had done it with the possible exception (in hindsight) of Paul Klimek, Bengt Magnusson, Bruce Tiemann, Mike Day, Adam Chalcraft, and me.

At the time it just wasn't known. When I was at juggling conventions I could torture 7 ball jugglers by getting them to try 441, 5551, and 66661. If you've never done SiteSwaps they feel seriously weird.

If that doesn't answer your question, tell me more about your background, what you know, whether you can juggle, and I'll tailor my answer further.

I know nothing of juggling; however, that 5551 was a previously unknown juggle was all I needed to know. Thanks!

There's an animation of 5551 here: https://juggle.fandom.com/wiki/5551

Actually, it's not just that it was unknown, it's also that it was particularly weird. It's not just a pattern, it's a cool pattern. Not just previously unknown, but of a previously unknown type.

That's what made it especially interesting.