They basically decided it was a deliberate high shot.
I think that is a very harsh interpretation.
The case wasn't put before the usual NRL tribunal. It was a special tribunal that had a rep from both Qld and NSW. I think it was so harsh because of sour grapes by the Qld rep on the tribunal. The tackle did cause them to lose one of their best forwards for much of the game, which had a big bearing on the final result.
I think that if he were tried before the usual ex-player, etc etc, they would have accepted his claim that the tackle was accidentally high and he would have got a much lighter suspension.