Well, presumably the rest of the team would push for increased monitoring and access control until coworker was no longer confident they could steal the bonus w

Well, presumably the rest of the team would push for increased monitoring and access control until coworker was no longer confident they could steal the bonus without getting caught, at which point your systems have been hardened and risk from outside attackers is also probably reduced. But, I'm definitely getting into 'hand wavy' territory here.