Americans are getting so used to complex answers (favored in news media and movies precisely because such things are rare) that they can't seem to accept simple straightforward answers. Follow Occam's Razor.
Kind of a reverse Payne Stewart..
WTC were symbols for us that got the world's attention. Crashing a plane into any building in Italy...hrmmm..what is a big symbol in Italy, that would get the attention of the world, and make a point....hrmmm...isn't there someplace around Rome that is a big symbol to many many people...oh yeah, the VATICAN! Do they waste a good-sized airplane on a 30 story concrete tower in Milan, or go for the Vatican?
Following Occam's Razor here leads to the inevitable conclusion that it wasn't an accident, as it is far and away the simpler explanation.
Pace the hyperventilating media, there are few if any confirmed facts in this matter. We don't know who was flying the plane, what kind of plane it was, who else was in it, etc.