The title is missleading. I didn't see anywhere in the article that pointed to the "real reason...".
Some news sources have consistently misreported this as saying that they were being tried for "failing to predict the earthquake". That would, of-course, be nonsense as no-one can predict when an earthquake might strike. However, that is not what the prosecution said - their case was based on the scientists failing to communicate risk properly.
Quoting the source: "The verdict was based on how they assessed and communicated risk before the earthquake that hit the city of L'Aquila on 6 April 2009, killing 309 people"
That was the real reason.