What do u think ended Finny's self-protective fantasies about war and the olympic games??

I think that Leper's demise as well as Finny's understanding about the chronic state of his injury makes him give up on life. As soon as Gene tells them about Leper, Finny seems to have automatically changed. When Brinker makes a remark about Finny being crippled and sidelined, Finny just accepts the remark, rather than giving Brinker heck for saying such a thing. When Gene urges Finny to say that there isn't a war, Finny obliges him, but his completely ironic statement betrays that he no longer believes in his own fantasy-world constructions.