I mean the "Illuminati" was a legitimate secret society in Europe in the late 1700s. That's likely why the name still remains in modern cult legends, or they're still at it. Who knows. I think the bigger issues are the elephants in the room like Black Rock, and Raytheon, BP, etc. like the evil fuckers are working out in plain day, they don't really need to be secret. It might not be as romantic as a secret cabal of occult practitioners as it is just a bunch of rich sociopaths.
And yeah. I think it's just power that corrupts people. From the dawn of time we have stories of rich assholes hurting poor people. We haven't really changed much in the last 4000 years except we have fancier toys, more food, and get to sit down and slowly damage our retinas in the majority of our free time.