They sold millions due to marketing and hype but most realize what a piece of useless shit it was. Apple fucked up by not making it worth under $100 and something maybe all iphone owners would buy, but wanting too much money was it's downfall.
I haven't seen it as a downfall yet.
I'm not saying it's a great product, I don't have one.
I can't say it's a failure though... If you make a billion dollars on any single product, it's not a failure.
I don't play Clash of Clans, but they made a billion dollars last year, I think the game is stupid, but it's not a failure.