Look, just watch the footage again. Those three decisive calls were even hard to judge with freaking replays. The first two, namely the Spinesi goal and the first Del Piero trip, were very hard to judge, and both players seemingly had half of their bodies on and offsides if you look at the grass lines.
The Del Piero penalty looked like a penalty but if you watch closely the defender, I think it was Biagianti, slightly touched the ball. The trip happened AFTER he touched the ball. Therefore not a penalty.
Either way, it was tough to call, but there is no conspiracy here. Case closed.
PS - Spinesi's goal was Molinaro's fault for even being there so close to Spinesi and not goal-side.