It's popular because it is *not* a blockchain.  It is distinctly different than all other crypto-currencies.  Like really, really different.  And it does not suffer from the problems that everything based on a blockchain has.

That said, it's still quite early, and the jury is out if the actual network meets the hype and marketing sales pitch we have all heard to date.

For me, it's the first alt-coin I have taken any real interest in because it is such a unique technology.