Frankie got lucky, the others just weren't smart enough to see it (game theory).
The Seer didn't ruin the game. The others failing to see the game theory did. Frankie actually got lucky picking Charlotte. The other faithfuls were too dumb to see it. Applying the prisoners dilemma would have shown them that Frankie is a faithful. It's the first proper piece of evidence they've actually had (except Alexander giving his coins to Frankie - another example of game theory).
Of the 4 combinations of roles available for Frankie and Charlotte, Frankie got lucky. The other 3 have too much cause for suspicion. She got the only one that proves she was a faithful.
The Seer didn't ruin the game. The others failing to see the game theory did. Frankie actually got lucky picking Charlotte. The other faithfuls were too dumb to see it. Applying the prisoners dilemma would have shown them that Frankie is a faithful. It's the first proper piece of evidence they've actually had (except Alexander giving his coins to Frankie - another example of game theory).
Of the 4 combinations of roles available for Frankie and Charlotte, Frankie got lucky. The other 3 have too much cause for suspicion. She got the only one that proves she was a faithful.