You must be relatively new to A2K.
You accomplished your stated purpose, but if you thought you were writing an essay that would somehow serve as a tribute, you picked the wrong forum.
This is a discussion forum, not a blog, and the whole idea of posting a thread herein is to get a discussion going.
The longest you can probably expect a thread to stay on it's original track is about 3 to 5 days. Most of them don't even last that long. Yours has been going for over a month now.
It's not easy to keep a thread on the originally intended track, but if you want to try, you have to work at it. I don't know that I've ever seen anyone succeed who only complained about it going off track.
If you realize you don't own any of the threads you launch here, you may enjoy the experience more.
Generally speaking the threads with the freshest subjects stay on track the longest. This was the 10th anniversary of 9/11. It's been discussed an awful lot since 2001. It's not like there are a lot of new angles.
When you sit down at a family dinner and start a coversation about something that happened to you at work that day, and an hour later you find you are all talking about something entirely different, do you get annoyed that everyone trashed your story?