Plot hole: I have never seen a Daytona 500 race where the winner is immediately left completely alone and is able to walk over to his crew chief who is still at the pit wall and hold a quiet conversation.
Plot hole: Paulie couldn't be that stupid so as to not tell Rocky that his accountant needed his signature for a tax extension.
Suggested correction: Paulie isn't exactly a Rhodes Scholar. I doubt he has any formal education beyond high school. He likely has no knowledge whatsoever about what a power of attorney is or what it does. Very easy to trick.
And furthermore, Paulie couldn't have had anyone sign anything on Rocky's behalf. Once it's proven in court that someone forged Rocky's signature, then everything would have been reversed and he would have never lost his fortune. If this was that easy, then anyone could walk into an office claiming to know a billionaire, sign a piece of paper, and get all their money.