Intelligence is the ability to develop plans that will get you what you want in the most general way possible.
The more general the methodology is to develop plans that will get you what you want, the more intelligent you are.
Some people, however unintelligent yet charismatic, have the ability to spew keywords that will get various kinds of homo sapiens to dumbly nod their head and give them what they want.
Often this merely involves them thinking you have money, in the echoing false assumption that somehow some of that money will be theirs.
This is not intelligence. This is just well placed stupidity. And evil.
Other times, there's something much more cunning in that seat, and it doesn't give a shit that the party's gonna end because they're gonna have a good time, and they have already spawned but "who cares, fuck em". Even so, it works hard, plans plans, sees what shit it can fuck up.
This IS intelligence. And evil.
Some people like chaos and don't care who it hurts.
I recognize this as someone who likes chaos a bit too much themselves, and does care.
Think of someone you find intelligent, and disturbingly so, and think what they could do if they just didn't care about consequences and they were insulated from people who might?
That's what's going on here and thinking they're stupid just because they are brazenly evil does not fly well.
Someone can be a fucked up, intelligent evil monster.