Satan only "rules" because people are too weak to resist his attempts to rule and control them.
He's a mind-reader, sifting peoples thoughts to pick up on their character flaws to use against them, then injecting custom-made poisonous "seeds" into their minds.
He tries it with all of us, for example Jesus said to Peter-
"Satan wanted to sift you" (Luke 22:31)
Atheists are the easiest meat for Satan because they don't believe he exists and therefore can't defend against him.
He's also good at influencing organised religions and cults; for example he's convinced catholics to waste prayers on Mary instead of God, and convinced cultists that they know more than the rest of us.
Jesus said-
"Satan has no hold on me" (John 14:30),
so all we can do is try to be like him and take this advice-
"Don't give the devil a foothold" (Eph 4:27)
"Resist the devil and he'll flee from you" (James 4:7)
Satan in 'The Passion', always slyly lurking, planning, scheming..