That was a long read... though interesting. I'll start a little aside. It IS in human nature to kill and go to war. Since people of all nations do that to some extend, it is in their nature. And if you want to see nature and pleasure of violence and murder, just watch kids, watch bullies, they appear in most of groups of kids and also see how kids treat animals. It is empathy and gentleness they have to learn hard way. Becoming peaceful person who tamed that warlike ancient nature of ours, but also is helping the world, is one who was raised above basic human nature. This nature we got from our ancestors, before humans were humans, they were already predators hunting and killing animals and that is still in our blood.
But later when humans became humans, some became noble and some very wretched. These evil people didn't stop being evil, they became evil spirits, we can call them demons, angels then are noble humans who evolved that way. Human souls reincarnate and so even these noble and wretched ones are still here, reincarnating and manipulating.
Same as for every other soul. Narcisists, I assume we can imagine cult leaders, are people who were doing this game for lifetimes. Their skills honed for centuries. I don't know if there even is any end goal, but there is surely path and desire for power, a bottomless cup of desire for more power.
My theory is that for example Mohammad, and I do not intent offense, this is just what I think, simply keeps reincarnating too, just like everyone else. He was a leader of religious community with taste for political power. Later he might had been reborn as the Old Man, Hassan-i-Sabbath, founder of Assassins, later he might had been Josef Smith... and the path goes ever on and he walks the Earth again, most likely... Souls do not change that much, especially if doing something they enjoy doing, then they do it life after life after life... But they tend to improve.
"Bright, Loving souls" are not defenseless any more than any other souls. Loving doesn't means stupid or blind. In fact, people falling for narcissists and their cults are people who happen to be weak in some way, wounded souls, suffering silently and finding group, that love-bombs them or uses any other tactics to make them feel welcome, to make them feel that they finally found home. And these cults are targeting such people, because they know that they are possible converts. They and the kids.
Narcissists, I wonder if there is anyone above them controlling them. The nature of Narcissists being "Me, me, me, me, me!" doesn't sound like allowing for that, although it is possible. (I think it's very unlikely) But they love to control, because it feels good to them, they do what they love to do. They do not seek "bright, loving" souls, they seek souls that they can control.