> My theory is every so often someone stumbles upon it, thinks “oh that’s interesting!” and submits it, not realizing it’s a duplicate? ..and then tons of readers in the same boat upvote it?

The social bug being that you keep getting older and there is always young newcomers that don't have the knowledge you have already picked up?

https://www.youtube.com/watch?v=9gWtrnb4KjU