I appreciate the analytical approach to this. I've always thought it was strange how much they're hated. I don't love their music, but at worst it seems unremarkable, with a few relatively decent songs thrown in.
I read once - I don't know if it's true - that there was a compilation CD made of a bunch of Metal bands (a marketing thing), and they put Nickelback song on it for some strange reason. Metal fans were outraged, and every time the CD was discussed, someone would say that Nickelback sucks, which contributed significantly. That would be another case of #4 on the list, if true.