Something short of "bigger than the internet" ("people familiar with the matter" really did call it that even before it was revealed what it was) can still be a popular product. In recent years, as commented here, there were a bunch of new entrants to the category, so yes it was useful to somebody.

Did it? That's news to me. I've only ever seen the Segway used for city tours. I've honestly never seen it in a different context. Seems like a marginal use of a marginal tech to me...

Edit: I lie! I once saw it used by a kids' magician at a birthday party. Pretty marginal use, too.

Going by anecdote, I've seen them used by many mall cops, city tours, downtown cops, some Taiwanese military unit used them as a meme, and some rich people here in the US owned them in their house literally just for fun. I think they were going for less than 10k used so that was play money for them.

Again, that they are going out of production shows that they are definitely not bigger than the internet. But they certainly aren't vaporware or even a failed product. Someone somewhere made a profit, and someone somewhere got non-zero utility out of it