In Axelrod's tournament, Tit-for-Tat never once scored more points than the strategy it was playing against. It won the tournament outright. How can a strategy that never beats a single opponent finish first?

D. Because the tournament scored total points, not head-to-head wins.

The result looks paradoxical only if you assume the game is a contest between the two players. It is not zero-sum: Tit-for-Tat never defected first, so the most it could do was match a cooperator, which is a high score for both. The exploiters collected small advantages and then met each other, where both scored badly.