Responsibility

To use brash words, this female Night Elf was neglected by her husband, and hence, went and looked for C'Thun out of loneliness.

Of course, in reality it was actually the Old Gods that had corrupted her mind and brought her into an evil cult. This type of backstory was often seen in Dawn. The most famous one was probably of how Sargeras had become a fallen titan.

These characters didn't lose their minds, which was different to the Undead. They still held their strong beliefs, and they were even stronger than before, but it was the content of their belief that was twisted.