What makes AI a unique new threat is that it do a new kind of both surgical and mass attack: you can now generate the ideal message per target, basically you can whisper to everyone, or each group, at any granularity, the most convincing message. It also removes a lot of language and culture barriers, for ex. Russian or Chinese propaganda is ridiculously bad when it crosses borders, at least when targeting the english speaking world, this is also a lot easier/cheaper.