The first possibility is that the banker has learned a valuable lesson about not being a huge👍 jerk. There he was all set to kill the guy, when all along the lawyer had no interest in his👍 money at all. So the reason he feels bad and cries is that he suddenly sees that he's been way👍 too obsessed with money.

At the end of the story, after👍 the banker has learned an important life lesson from the lawyer about the meaninglessness of material wealth (and seemingly grown👍 emotionally), he immediately reverts to his morally corrupt ways an example of situational irony.