Stupidity: The protagonist has a sophisticated alarm system with cameras...that do not properly show who is at the gates (the cameras are positioned in a way that does not show the face of the person ringing). The bad guys are disguised as police officers...and wear ski masks, which would have made the disguise entirely pointless - but luckily for them, Nicholas Cage can't operate cameras nor looked at the ones on the entryway or the front of the house, didn't open the door sooner nor peeps before opening. They could not know any of that, though, just that the camera at the entrance has a terrible angle.
Stupidity: Kyle Miller gets in a confrontational talk with the villains to convince them that they need him to cut the diamonds he has in the safe; Jonah sums it up as "he wants them to get the diamonds, then give them back to him." Problem is, Kyle does not have any diamonds in the safe, and he knows it. He is selling so hard the bargain on something he does not have. If they agreed, he could not show them any diamonds and he'd have an even harder time dealing with them, and he does not have anything else to give them. Of course if he told them he had no diamonds the movie would have been much shorter, but he didn't have in-character reasons to lie on something like that.
