My takeaway from this is that the founders wanted to get into YC. The business doesn't matter, they just wanted to be in YC.
The business morphed around what they thought would get into YC, not what would actually make a good business. I have a ton of respect for YCombinator, but they are not all knowing oracles who get it right 100% of the time. The fact that the immediate response to each rejection was "pivot" I think speaks volumes to the founder's goals here.