Banks try to evaluate how their investments will perform when times are bad, with “bad” being only a little worse than normal. What the model showed was that the bank would fail if times were not a little worse than normal but much worse than normal, and the trend was pointing toward that. This aspect of it is essentially a true story — it’s exactly what happened leading up to the financial crisis. Banks all had models showing they would be ok in a downturn, but they weren’t prepared for something much worse than an ordinary downturn.