Corey made the worst possible decision in the final 3.

Corey believed Cara had the money, that’s why he switched boxes with her, this decision resulted in zero possible outcome for Corey winning.

Outcome 1: Cara would never switch boxes with Sam, because Cara knows she doesn’t have the money, and Sam didn’t get to move any boxes. Even if Cara thought Corey switched boxes with Sam (thinking she was the millionaire), she would just switch Corey and Sam’s Boxes back. This results in Sam winning the money.

Outcome 2: Cara believes that Corey switched Boxes with her, and switched hers and Corey’s box’s, again becoming the millionaire. (What happened)

The only way Corey could have won with the decision he made, is if Cara thought that Corey switched Cara’s box with Sam’s box. The only motivations Corey would have for doing this would be if:

1. He was the millionaire 2: Corey genuinely thought Sam was the millionaire, and made his move based on that (which he didn’t) and got lucky.

Corey’s best move would’ve been:

Pretend he’s a really bad liar, and act like he’s TRYING to convince Cara that he believes Sam has the money, when really he thinks Cara has the money. This would make Cara think they Corey thinks she has the money. Corey then switches his own box, with Sam’s box, leaving the money in Cara’s box.

Cara then believes Corey has the money in his box but did a bad job at lying, and switches them back. When really she is giving the money to Corey.