Raising money, at least initially, is about two things: user traction and good PR. I don't know how many users Ello has, but I've personally been hearing about them all over the place, especially from my early-adopter type friends on Facebook. This leads me to believe that the company has a really good PR firm working for them behind the scenes (PG's "submarine" analogy comes to mind).
And the thing is, Ello may be hard on the eyes and not be very usable now, but both of those things are relatively easy to improve. If they do have good user traction, that means they have solved the hardest problem, at least in my opinion. Achieve growth and the rest follows rather naturally.
Pretty & usable are easily purchased. Throw an expensive dev team at it. Brand and reputation are more difficult.