I agree with Rattus' point upthread, that the subjective criteria allowed Trump to hand the win over to Joan. Why he wanted her to win, however, is curious. This is a man who measures everything by money, because that's the scorecard on whether someone's a winner or a loser. And he's got a thing about winners and losers.
In every past season he's rewarded ruthlessness and manipulation and punished selflessness. Annie is probably the most Trump-like player to ever compete ... and she loses? It doesn't make sense.
That said, as emotional and angry as Joan can get, I'm like the gay guy at his mother's funeral ... I think she'd be a total hoot as a friend.