In that scene, Johnny Caspar is basically struggling with who to believe. As kingpengvin points out, Eddie Dane has already tried to sell Caspar on the idea of a double-cross, even though Tom seems to be playing it straight with Caspar. In Caspar’s mind, I think this is especially evident in the way that Tom immediately forks up the info on where Bernie is hiding when he first goes to Caspar after Leo kicks him out.
Eddie Dane tailed Tom and picked up Drop Johnson, beat him up and interrogated him – finding out the truth, which is that Tom didn’t kill Bernie. However, at this point, Tom has already insinuated to Caspar that not only has Mink been selling him out (which is true), but that also Eddie Dane is in on selling out his fixed fights (which is not true). But Caspar already sees possible motive, and coupled with the fact that The Dane has already pushed for a double-cross (and Caspar doesn’t care for double-crosses on somebody who shows you good faith), he believes Tom at the end. Clearly he is struggling with who to believe during the confrontation between Tom and Eddie Dane.