Since you can read minds perhaps you can tell us what the marketing team was thinking?
Or, just maybe, it sold better in some areas, worse in others and, possibly,
100 locations is a fraction of the total retailers that stocked the sets, which doesn't even take into account online purchases,
how many of the stores that still have bionicle are toysrus? Because they have their own problem with sales in general and I wouldn't account the remaining stock on bionicle, at least not fully.
It most likely sold averagely, but couldn't keep up sales because of the awful marketing, I don't believe it was the train wreck you're suggesting,
but rather it simply fell short of what Lego considered necessary to continue early on(2nd wave) so they cancelled the line early to try to save the brand.
Regardless, we don't know, all we know is that Lego said it was selling well, not great, not exceptionally, well, and that, from anecdotal evidence, it was selling fine in some areas and poorly in others.
which makes me believe that it sold averagely but began to decline, and Lego decided to cut it early to minimize any potential losses.