They got it wrong multiple times though. Maybe adjust the models after you got it wrong twice? And they didn't get it wrong just a bit, their most optimistic projection got it wrong by orders of magnitude. If we look at the paper, they actually show what are more realistic projections are.
I'm not sure if malice or incompetence is really a better judgement of the work though.
But they weren't predictions were they? They were forecasts based on the current policies at the time. So basically a warning to govs that more policies were required to sustain growth...
Nearly nobody in an industry that manufactures goods can foresee a way to sell the goods they make for less than ~half of what they currently sell for. Yet sometimes prices can go down by a factor of 10x or 100x or more in ways few predict.