I think you are right. To many people open themselves up for it and don’t even realize they’ve done it. Also just plan sin, although I do think quite often when it’s extreme it’s demonic. Sin starts in the thoughts, that’s why Jesus told us to take captive ever thought to the obedience of Christ.
Demon possession...
One thing that has struck me for quite awhile, is how many murders and serial killers who later came to faith in Christ believed that they were demon possessed when they were killing.
David Berkowitz, Henry Lee Lucas, Jeffery Dahmer, and several of the Manson family members.