You knew your opponent had a Possession in hand/was likely to play one, and after playing all the actions in an engine turn
1. Bought 2 Curses
2. Overpayed for a Doctor, triggering a reshuffle of junk cards, or overpay for Herald to topdeck junk cards.
letting you organize a hand that's useless when Possessed. You wanted Curses over Coppers because you actually needed to make sure opponent didn't get that extra $2, and you needed exactly 2 more junk cards to guarantee a dud. The problem is that if your opponent doesn't play Possession, you've put yourself behind, so this doesn't make much sense to me - you'd need your dud hand to have just enough money to make you win, but not enough to have the opponent win.