Some people amassed a small bunch of delegations while the system was new and interesting, then usage dropped off. Since the delegations didn't expire, individual votes didn't matter - these "super delegates" had so much voting power that they'd generally outvote the remaining active users of the system. Combine this with the high cost of participating yourself (you need to repeatedly inform yourself and engage with the system) compared to delegation (just pick a person that seems reasonable once and forget it).
The lack of having any meaningful voice further discouraged people from participating, both in the system and the party as a whole. It sounds good in theory, but I'm not sure this practical hurdle can be overcome. There will usually be a majority of mostly passive users, and the corrective power of Liquid Democracy ignores this and assumes users change their vote if their delegate votes against their interest.
The Swiss system (a sufficiently large group of people can initiate a referendum or popular initiative, then the matter is put to a one-person-one-vote vote) seems like a very practical solution to the problem where you want the "boring" decisions handled by someone else, while keeping them in check and allowing controversial decisions to be overturned.