I don’t know what the facts are in this regard and you don’t either. But your reaction strikes me as knee-jerk and premature. There are certainly plenty of cases of Iran working with Sunni groups (e.g., Hamas). We’ll have to see how the information develops but you don’t sound like you have any interest in the information.
It also need not turn out (I don’t know) that Iran was hand-in-glove with Al Qaeda all the way through. They may simply have provided some specific kinds of assistance (what has long been alleged such as easing travel of Al Qaeda operatives through Iran to Afghanistan etc.). It may or may not turn out to have been any direct planning role from Iran, but to rule it out without knowledge is unwise in light of Iran’s long history of terrorism operations.
I’ve only just found this website so I’ve only glanced at it so far, but it seems to have a lot of info about the legal case: