The early years were very influenced by Maori culture in terms of the names and the island setting, but the overall Bionicle story was almost completely separate, conceived by Christian Faber and some other creatives.
Given the topic title, it's his opinion that the brittle pieces were the biggest disappointment, while it might be someone else's opinion that the biggest was something different.
It made sense not to name it, given that it plays no part at all in the movie story, which is all about (in addition to the Toa) Lhikan, the Dark Hunters, Dume and Makuta.
Its 'cameo' was just a little reference for those who knew the full story.
As Master Inika said, pretty much every television show loses viewers sooner or later.
It's a particular problem for story-based shows, because the further on it goes the more difficult it is for new viewers to grasp what's happening.